Thank you everyone for the comments. I decided to use Russell's idea combined with Jan's clearing beforehand.

Sorry for waiting so long to reply. I got a little bit side tracked.

Here is updated code

; GET DIFFERNCE BETWEEN OLD AND NOW
GETDIFFERENCE:  MOV A,R1               ;R1 IS OLD 
                
OldGreaterThanNow: CLR C
                   SUBB A, R0
                   
                  JC OLDLESSTHANNOW ;if carry set new > old &jump  
                  JZ FINISH          ; JUMP TO END a=0
                   MOV R5,A          ;R5 = # OF TIMES TO RUN LOOP
                   MOV A,R0          ;R0 = NOW 
                   MOV R1,A          ;R1 = OLD 

                 ;NOW SET DI BIT AND RUN LOOP FOR A# OF TIMES
                   SETB DI
                   DJNZ R5,LOOP
                   JMP MAIN

OldLessThanNow:    MOV A,R0
                   SUBB A, R1
                   MOV R5,A ;        R5 = # OF TIMES TO RUN LOOP
                   MOV A,R0 ;R0 = NOW
                   MOV R1,A ;R1 = OLD

                  ;NOW SET DI BIT AND GO TO LOOP FOR A# OF TIMES
                   CLR DI
                   DJNZ R5,LOOP
                   JMP MAIN

Regards,
Steve