%EQUAL in a DOU loop

Hello,

The program seems to crash in the routine below.  I know that there aren't any 
records with 999 lines of notes.  I'm thinking that maybe the program
keeps looping.
Am I missing something in the code below that would cause this routine to keep 
looping?

The program crashes with this message, "Receiver value too small to hold result.
The target for a numeric operation is too small to hold the result"

Thanks,

Frank

C                   EVAL      KF_LINE = 1
 *
 * Set File Pointer
C     FILEKEY15     SETLL     FILE15
 *
 * Notes Records Exist in File
C                   IF        %EQUAL(FILE15)
 *
 * Find New Line # for Note #
C                   DOU       NOT %EQUAL(FILE15)
C     FILEKEY15     SETLL     FILE15
 *
C                   IF        NOT %EQUAL(FILE15)
C                   LEAVE
C                   ENDIF
 *
C                   IF        %EQUAL(FILE15)
C                   EVAL      KF_LINE = KF_LINE + 1
C                   ENDIF
 *
C                   ENDDO