>so how should I write codes according to your given line
>
>padr(value, LensetBeforeLoopAccordingToFieldLen)

Select Master
if tagno("codes")=0
   index on codes tag codes
endif
if tagno("pqty")=0
   index on pqty tag pqty
endif
Replace All pqty With qty  && index could hurt here - measure effect of 2. index!
lnLenMaster = len(codes)
....
** for loop to scroll on sales.dbf
select sales
for  && scan if possible
        cur_code = padr(codes, m.lnLenMaster)
        Select purchase
	Do While endloop>0  && move to scan if possible
		Select Master
		Locate For codes=m.cur_code And pqty>0
		If Found()
....
endfor && scan