Here is the standard way of approaching this problem

Re: Primary Keys Thread #441081 Message #441087

>Help. . . I have a little table which provides the next barcode number but I can't stop getting a duplicate number over the network. Sometimes when two or more people are using the system and generating new barcodes, we get duplicate numbers. Here is my barcode numbrs code :
>
>

>local nBarc
>select barcno   && table with barcode number
>nBarc=barcno.barcno  
>IF nBarc <= 0
>	MESSAGEBOX("This computer is not setup with barcode numbers","")
>	RETURN
>ENDIF 	
>replace barcno with nBarc+1  &&increase by one
>FLUSH in barcno force   
>IF USED("barcno")    && clos the table
>	USE IN barcno
>ENDIF
>IF NOT USED("barcno")  && open the table 
>	SELECT 0
>	USE barcno
>	
>endif		
>

>
>Any quick fixes ???
>Cheers. Shafid