Hi Greg, thank you for your reply. I can not lock the whole table because it is used for other things. But I tried to lock the record and pass the next barcode number but on occasions, the number was duplicated if two operators where working on the system. When I closed and open the table, plus the rlock(), it seems to behave and I haven't seen any duplicates yet. Here is my modified code :

IF USED("barcno")
	USE IN barcno
ENDIF
IF NOT USED("barcno")
	SELECT 0
	USE barcno
endif		
select barcno 

nBarc=barcno.barcno  
IF nBarc <= 0
	MESSAGEBOX("This computer is not setup with barcode numbers","")
	RETURN
ENDIF 
IF RLOCK('barcno')	
	replace barcno with nBarc+1
	UNLOCK
else 
       MESSAGEBOX("The barcodes numbering file is in use, plese try again","")
	RETURN
ENDIF 	
FLUSH in barcno force
IF USED("barcno")
	USE IN barcno
ENDIF