diff --git a/src/com/bytezone/diskbrowser/visicalc/Abs.java b/src/com/bytezone/diskbrowser/visicalc/Abs.java
index 09239ad..16d398c 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Abs.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Abs.java
@@ -16,6 +16,7 @@ public class Abs extends Function
     {
       source = new Expression (parent, functionText);
       values.add (source);
+      source.calculate ();
     }
 
     value = Math.abs (source.getValue ());
diff --git a/src/com/bytezone/diskbrowser/visicalc/Average.java b/src/com/bytezone/diskbrowser/visicalc/Average.java
index a4693a3..dde7ca5 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Average.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Average.java
@@ -7,7 +7,7 @@ public class Average extends Function
   public Average (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
   }
 
   @Override
diff --git a/src/com/bytezone/diskbrowser/visicalc/Cell.java b/src/com/bytezone/diskbrowser/visicalc/Cell.java
index 2fc47a9..465f7c5 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Cell.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Cell.java
@@ -81,6 +81,7 @@ class Cell extends AbstractValue implements Comparable<Cell>
     {
       expressionText = command;
       cellType = CellType.VALUE;
+      value = new Expression (parent, expressionText).reduce ();
     }
 
     // FUTURE.VC
@@ -144,7 +145,10 @@ class Cell extends AbstractValue implements Comparable<Cell>
 
       case VALUE:
         if (!isValueType (ValueType.VALUE))
-          return Format.justify (value.getText (), colWidth, 'R');
+        {
+          char fmt = cellFormat != ' ' ? cellFormat : globalFormat;
+          return Format.justify (value.getText (), colWidth, fmt);
+        }
 
         char formatChar = cellFormat != ' ' ? cellFormat : globalFormat;
         return " " + Format.format (value, formatChar, colWidth - 1);
@@ -158,8 +162,10 @@ class Cell extends AbstractValue implements Comparable<Cell>
   @Override
   public double getValue ()
   {
-    if (value == null)
-      calculate ();
+    //    if (value == null)
+    //      calculate ();
+    if (cellType != CellType.VALUE)
+      return 0;
 
     return value.getValue ();
   }
@@ -167,14 +173,21 @@ class Cell extends AbstractValue implements Comparable<Cell>
   @Override
   public ValueType getValueType ()
   {
+    //    if (value == null)
+    //      calculate ();
+    if (cellType == CellType.EMPTY)
+      return ValueType.NA;
+
     return value.getValueType ();
   }
 
   @Override
   public String getText ()
   {
-    if (value == null)
-      calculate ();
+    //    if (value == null)
+    //      calculate ();
+    if (cellType == CellType.EMPTY)
+      return "";
 
     return value.getText ();
   }
@@ -182,9 +195,15 @@ class Cell extends AbstractValue implements Comparable<Cell>
   @Override
   public boolean isValueType (ValueType type)
   {
-    if (value == null)
-      calculate ();
+    //    if (value == null || value.getValueType () != ValueType.VALUE)
+    //      calculate ();
+    if (cellType == CellType.LABEL || cellType == CellType.REPEATING_CHARACTER)
+      return type == ValueType.VALUE;
 
+    if (cellType == CellType.EMPTY)
+      return type == ValueType.NA;
+
+    assert value != null : "bollocks " + address;
     return value.isValueType (type);
   }
 
@@ -196,20 +215,15 @@ class Cell extends AbstractValue implements Comparable<Cell>
   @Override
   public void calculate ()
   {
-    if (value != null && value.isValueType (ValueType.VALUE))
-      return;
+    //    if (value != null && value.isValueType (ValueType.VALUE))
+    //      return;
+    //
+    //    if (expressionText == null)
+    //      expressionText = "";
 
-    if (value == null)
-    {
-      if (expressionText == null)
-        expressionText = "";
-
-      value = new Expression (parent, expressionText).reduce ();
-    }
-
-    value.calculate ();
-
-    return;
+    //    value = new Expression (parent, expressionText).reduce ();
+    if (value != null)
+      value.calculate ();
   }
 
   public String getDebugText ()
diff --git a/src/com/bytezone/diskbrowser/visicalc/Choose.java b/src/com/bytezone/diskbrowser/visicalc/Choose.java
index 2f40660..f5eaa00 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Choose.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Choose.java
@@ -14,7 +14,7 @@ public class Choose extends Function
     int pos = text.indexOf (',');
     sourceText = text.substring (8, pos);
     rangeText = text.substring (pos + 1, text.length () - 1);
-    range = new Range (rangeText);
+    range = new Range (parent, rangeText);
     source = new Number (sourceText);
   }
 }
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Count.java b/src/com/bytezone/diskbrowser/visicalc/Count.java
index d80d912..5211bfd 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Count.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Count.java
@@ -7,7 +7,7 @@ class Count extends Function
   public Count (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
   }
 
   @Override
diff --git a/src/com/bytezone/diskbrowser/visicalc/Expression.java b/src/com/bytezone/diskbrowser/visicalc/Expression.java
index b335a19..8d04b13 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Expression.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Expression.java
@@ -74,9 +74,9 @@ class Expression extends AbstractValue implements Iterable<Value>
               bracketText.substring (1, bracketText.length () - 1)));
           break;
 
-        case '#':
+        case '#':                                           // no idea
           System.out.printf ("Hash character [%s] in [%s]%n", ch, line);
-          ptr++;                                            // no idea
+          ptr++;
           break;
 
         default:
@@ -93,8 +93,9 @@ class Expression extends AbstractValue implements Iterable<Value>
             Cell cell = parent.getCell (addressText);
             if (cell == null)
             {
-              System.out.println ("adding NA");
-              values.add (Function.getInstance (parent, "@NA"));
+              // should this (or parent) create a new empty cell?
+              //              cell = parent.addCell (addressText);
+              values.add (new Number ("0"));
             }
             else
               values.add (parent.getCell (addressText));
@@ -154,17 +155,18 @@ class Expression extends AbstractValue implements Iterable<Value>
     try
     {
       Value thisValue = values.get (0);
-      thisValue.calculate ();
+      if (thisValue != null)    // || thisValue.getValueType () != ValueType.VALUE)
+        thisValue.calculate ();
 
       value = 0;
-      if (thisValue.isValueType (ValueType.VALUE))
-        value = thisValue.getValue ();
-      else
+      if (!thisValue.isValueType (ValueType.VALUE))
       {
         valueType = thisValue.getValueType ();
         return;
       }
 
+      value = thisValue.getValue ();
+
       String sign = signs.get (0);
       if (sign.equals ("(-)"))
         value *= -1;
@@ -172,17 +174,18 @@ class Expression extends AbstractValue implements Iterable<Value>
       for (int i = 1; i < values.size (); i++)
       {
         thisValue = values.get (i);
-        thisValue.calculate ();
+        if (thisValue != null)    // || thisValue.getValueType () != ValueType.VALUE)
+          thisValue.calculate ();
 
-        double nextValue = 0;
-        if (thisValue.isValueType (ValueType.VALUE))
-          nextValue = thisValue.getValue ();
-        else
+        if (!thisValue.isValueType (ValueType.VALUE))
+        //        if (thisValue.isValueType (ValueType.ERROR))
         {
           valueType = thisValue.getValueType ();
           return;
         }
 
+        double nextValue = thisValue.getValue ();
+
         sign = signs.get (i);
         if (sign.equals ("(-)"))
           nextValue *= -1;
diff --git a/src/com/bytezone/diskbrowser/visicalc/Int.java b/src/com/bytezone/diskbrowser/visicalc/Int.java
index 30a504b..e847a08 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Int.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Int.java
@@ -2,17 +2,21 @@ package com.bytezone.diskbrowser.visicalc;
 
 public class Int extends Function
 {
+  Expression source;
 
   Int (Sheet parent, String text)
   {
     super (parent, text);
+
+    source = new Expression (parent, functionText);
+    values.add (source);
   }
 
   @Override
   public void calculate ()
   {
-    Expression exp = new Expression (parent, functionText);
-    value = (int) exp.getValue ();
-    valueType = exp.getValueType ();
+    source.calculate ();
+    value = (int) source.getValue ();
+    valueType = source.getValueType ();
   }
 }
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Lookup.java b/src/com/bytezone/diskbrowser/visicalc/Lookup.java
index 5cbdfcd..29bfe80 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Lookup.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Lookup.java
@@ -13,26 +13,29 @@ class Lookup extends Function
 
     int pos = text.indexOf (',');
     sourceText = text.substring (8, pos);
+    source = new Expression (parent, sourceText);
+    values.add (source);
     rangeText = text.substring (pos + 1, text.length () - 1);
-    range = new Range (rangeText);
+    range = new Range (parent, rangeText);
   }
 
   @Override
   public void calculate ()
   {
-    if (source == null)
-    {
-      source = new Expression (parent, sourceText);
-      values.add (source);
-    }
-
     source.calculate ();
+
     if (!source.isValueType (ValueType.VALUE))
     {
       valueType = source.getValueType ();
       return;
     }
 
+    if (range.size () == 0)
+    {
+      valueType = ValueType.NA;
+      return;
+    }
+
     double sourceValue = source.getValue ();
     Address target = null;
 
@@ -44,15 +47,26 @@ class Lookup extends Function
       target = address;
     }
 
+    //    System.out.printf ("*****-----**** %s%n", target);
     if (target == null)
       valueType = ValueType.NA;
     else
     {
       Address adjacentAddress =
           range.isVertical () ? target.nextColumn () : target.nextRow ();
-      Cell adjacentCell = parent.getCell (adjacentAddress);
-      value = adjacentCell.getValue ();
-      valueType = ValueType.VALUE;
+
+      if (parent.cellExists (adjacentAddress))
+      {
+        Cell adjacentCell = parent.getCell (adjacentAddress);
+        if (adjacentCell != null)
+          value = adjacentCell.getValue ();
+        valueType = ValueType.VALUE;
+      }
+      else
+      {
+        value = 0;
+        valueType = ValueType.VALUE;
+      }
     }
   }
 
diff --git a/src/com/bytezone/diskbrowser/visicalc/Max.java b/src/com/bytezone/diskbrowser/visicalc/Max.java
index a9afee6..e698492 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Max.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Max.java
@@ -7,7 +7,7 @@ class Max extends Function
   public Max (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
   }
 
   @Override
diff --git a/src/com/bytezone/diskbrowser/visicalc/Min.java b/src/com/bytezone/diskbrowser/visicalc/Min.java
index d80c4ce..b7ef5d2 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Min.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Min.java
@@ -7,7 +7,7 @@ class Min extends Function
   public Min (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
   }
 
   @Override
diff --git a/src/com/bytezone/diskbrowser/visicalc/Npv.java b/src/com/bytezone/diskbrowser/visicalc/Npv.java
index 83d706a..9ae69ea 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Npv.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Npv.java
@@ -11,7 +11,7 @@ public class Npv extends Function
   Npv (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
 
     //    int pos = text.indexOf (',');
     //    valueText = text.substring (8, pos);
diff --git a/src/com/bytezone/diskbrowser/visicalc/Range.java b/src/com/bytezone/diskbrowser/visicalc/Range.java
index b8574b1..70f95b2 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Range.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Range.java
@@ -15,24 +15,41 @@ class Range implements Iterable<Address>
 
   Address from, to;
   List<Address> range = new ArrayList<Address> ();
+  Sheet parent;
 
-  public Range (String rangeText)
+  public Range (Sheet parent, String rangeText)
   {
+    this.parent = parent;
     setRange (rangeText);
+
+    createCells ();
   }
 
-  public Range (Address from, Address to)
+  public Range (Sheet parent, Address from, Address to)
   {
     this.from = from;
     this.to = to;
+    this.parent = parent;
 
     addRange ();
+
+    createCells ();
   }
 
-  public Range (String[] cells)
+  public Range (Sheet parent, String[] cells)
   {
+    this.parent = parent;
+
     for (String s : cells)
       range.add (new Address (s));
+
+    createCells ();
+  }
+
+  private void createCells ()
+  {
+    for (Address address : range)
+      parent.getCell (address);
   }
 
   private void addRange ()
@@ -54,6 +71,7 @@ class Range implements Iterable<Address>
       }
     else
       throw new InvalidParameterException ();
+
     from = tempFrom;
   }
 
@@ -77,6 +95,17 @@ class Range implements Iterable<Address>
     return range.iterator ();
   }
 
+  public int size ()
+  {
+    int total = 0;
+
+    for (Address address : range)
+      if (parent.getCell (address) != null)
+        ++total;
+
+    return total;
+  }
+
   private void setRange (String text)
   {
     Matcher m = rangePattern.matcher (text);
diff --git a/src/com/bytezone/diskbrowser/visicalc/Sheet.java b/src/com/bytezone/diskbrowser/visicalc/Sheet.java
index fd39181..41f985f 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Sheet.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Sheet.java
@@ -164,6 +164,7 @@ public class Sheet
       ptr += length + 1;            // +1 for end-of-line token
     }
 
+    System.out.println ("** Start of calculation **");
     // might have to keep recalculating until nothing changes??
     if (recalculation == 'A')             // auto
     {
@@ -260,6 +261,7 @@ public class Sheet
 
   private void addCell (Cell cell)
   {
+    //    System.out.printf ("Adding: %s%n", cell);
     rowOrderCells.put (cell.getAddress ().rowKey, cell);
     columnOrderCells.put (cell.getAddress ().columnKey, cell);
 
@@ -274,7 +276,19 @@ public class Sheet
 
   Cell getCell (Address address)
   {
-    return rowOrderCells.get (address.rowKey);
+    Cell cell = rowOrderCells.get (address.rowKey);
+    if (cell == null)
+    {
+      //      System.out.printf ("cell not found, creating: %s%n", address);
+      cell = new Cell (this, address);
+      addCell (cell);
+    }
+    return cell;
+  }
+
+  boolean cellExists (Address address)
+  {
+    return rowOrderCells.get (address.rowKey) != null;
   }
 
   public int size ()
diff --git a/src/com/bytezone/diskbrowser/visicalc/Sum.java b/src/com/bytezone/diskbrowser/visicalc/Sum.java
index ecac450..5b4d4eb 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Sum.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Sum.java
@@ -7,7 +7,7 @@ class Sum extends Function
   public Sum (Sheet parent, String text)
   {
     super (parent, text);
-    range = new Range (text);
+    range = new Range (parent, text);
   }
 
   @Override