diff --git a/auxmem.hostfs.s b/auxmem.hostfs.s
index 9a3f327..48b7dd8 100644
--- a/auxmem.hostfs.s
+++ b/auxmem.hostfs.s
@@ -60,11 +60,23 @@ OSFINDRET    >>>   ENTAUX
              RTS
 
 * OSGBPB - Get/Put a block of bytes to/from an open file
-GBPBHND      LDA   #<OSGBPBM
-             LDY   #>OSGBPBM
-             JMP   PRSTR
-OSGBPBM      ASC   'OSGBPB.'
-             DB    $00
+GBPBHND      PHX
+             PHY
+             PHA
+             JSR   XYtoLPTR                  ; Copy control block to GBPBBLK ..
+             LDY   #$0C                      ; .. in main memory
+             >>>   WRTMAIN
+:L1          LDA   (OSLPTR),Y
+             STA   GBPBBLK,Y
+             DEY
+             BNE   :L1
+             >>>   WRTAUX
+             PLA                             ; A represents the command
+             >>>   XF2MAIN,GBPB
+OSGBPBRET    >>>   ENTAUX
+             PLY
+             PLX
+             RTS
 
 * OSBPUT - write one byte to an open file
 BPUTHND      PHX
diff --git a/mainmem.fsequ.s b/mainmem.fsequ.s
index 743647a..077edfe 100644
--- a/mainmem.fsequ.s
+++ b/mainmem.fsequ.s
@@ -15,7 +15,14 @@ CMDPATH     EQU   $0280       ; Path used to start Applecorn
 MOSFILE1    EQU   $0300       ; length + 64 bytes
 MOSFILE2    EQU   $0341       ; length + 64 bytes
 MOSFILE     EQU   MOSFILE1
-*                 $0382           ; $3C bytes here
+
+GBPBBLK     EQU   $0382
+GBPBHDL     EQU   $GBPBBLK+0  ; File handle
+GBPBDAT     EQU   $GBPBBLK+1  ; Pointer to data
+GBPBNUM     EQU   $GBPBBLK+5  ; Num bytes to transfer
+GBPBPTR     EQU   $GBPBBLK+9  ; File pointer
+GBPBEND     EQU   GBPBBLK+12
+*                 $038F       ; $2F bytes here
 *
 FILEBLK     EQU   $03BE
 FBPTR       EQU   FILEBLK+0   ; Pointer to name (in aux)
diff --git a/mainmem.svc.s b/mainmem.svc.s
index d61aec7..f638996 100644
--- a/mainmem.svc.s
+++ b/mainmem.svc.s
@@ -322,6 +322,14 @@ CFILE         >>>   ENTMAIN
               PLX
               BCS   FINDEXIT
 
+* ProDOS file handling for MOS OSGBPB call
+* A=1 : Write bytes to disk, using new seq pointer
+* A=2 : Write bytes to disk, ignoring seq pointer
+* A=3 : Read bytes from disk, using new seq pointer
+* A=4 : Read bytes from disk, ignoring seq pointer
+GBPB          >>>   ENTMAIN
+*             ...
+              >>>   XF2AUX,OSGBPBRET
 
 * ProDOS file handling for MOS OSBGET call
 * Returns with char read in A and error num in Y (or 0)