Trigger Buffer V4R5

["Kyle S. Goodwin" <gte465z@xxxxxxxxxxxxxxxx>]

I'm somewhat new to RPG and AS/400 programming in general, and I'm  
attempting to write a trigger program in RPG ILE with embedded SQL.   
I've been digging through the archives and found lots of info about  
the trigger buffer data structure.  First I mistakenly tried to use  
the new version (with I type members) before realizing that the  
structure was changed in V5R1.  My trigger should be *INSERT and  
*BEFORE on my CUSTOMERS file and the functionality I'm trying to  
accomplish is to find the maximum value in the CUSTID column or 0 if  
there are none, add 1 to it, and use this value as the CUSTID for the  
insert.  CUSTID is the physical file's key and it is defined as  
UNIQUE.  Below is my code to accomplish this task, I can't seem to  
figure out why it does not do what it is supposed to do.  (It gives  
me a duplicate key error when I attempt to insert, so I assume that  
it is not modifying the value properly.  I have attached the trigger  
using the ADDPFTRG command.)  Sorry for the long message.

==TRGHDR==


     DTRGBUFFER        DS
     D TFILENAME                     10
     D TLIBNAME                      10
     D TMEMNAME                      10
     D TTRGEVENT                      1
     D TTRGTIME                       1
     D TCOMMITLOCK                    1
     D TFILLER1                       3
     D TCCSID                         4B 0
     D TFILLER2                       4
     D TFILLER3                       4
     D TOLDRECOFF                     4B 0
     D TOLDRECLEN                     4B 0
     D TOLDNULLOFF                    4B 0
     D TOLDNULLLEN                    4B 0
     D TNEWRECOFF                     4B 0
     D TNEWRECLEN                     4B 0
     D TNEWNULLOFF                    4B 0
     D TNEWNULLLEN                    4B 0
     D RESERVED                      16
      *
     DTRGBUFFERLEN     S              4B 0

==CUSTOMERK==

     D*
     D/COPY QRPGLESRC,TRGHDR
     D*
     D* Record format for New and Old Records
     D*
     D OldRecord     E DS                  ExtName(CUSTOMERS)
     D                                     Prefix(O)
     D                                     Based(OldRecPtr)
     D*
     D NewRecord     E DS                  ExtName(CUSTOMERS)
     D                                     Prefix(N)
     D                                     Based(NewRecPtr)
     D*
     D* Record Layout for New and Old Null Maps.
     D*
     D OldNullMap      DS                  Based(OldNullPtr)
     D ONullFld                       1
     D NewNullMap      DS                  Based(NewNullPtr)
     D NNullFld                       1
     D*
     C     *ENTRY        PLIST
     C                   PARM                    TrgBuffer
     C                   PARM                    TrgBufferLen
     C*
     C                   EVAL      OldRecPtr = %ADDR(TrgBuffer) +  
TOldRecOff
     C                   EVAL      NewRecPtr = %ADDR(TrgBuffer) +  
TNewRecOff
     C*
     C                   EVAL      OldNullPtr = %ADDR(TrgBuffer) +  
TOldNullOff
     C                   EVAL      NewNullPtr = %ADDR(TrgBuffer) +  
TNewNullOff
     C*
     C/EXEC SQL
     C+  SELECT COALESCE(MAX(CUSTID), 0) + 1 INTO :NCUSTID FROM  
CUSTOMERS
     C/END-EXEC
     C*
     C                   EVAL      NNullFld = *OFF
     C                   EVAL      *INLR = '0'
     C                   RETURN

Thanks!

Kyle Goodwin