Jerry,
there is a difference between WHILE and FOR

while will stop if the first record inv=mkey is reached

IOW WHILE will not run through the whole table, FOR will.

Agnes

Update:

the first record not inv=mkey
>I wonder why these two codes show difference results:
>
>

>use sales in 0 alias sales
>select sales
>mkey='003333'
>disp PK for inv=mkey
>use in sales
>

>
>result:
>--------
>0001
>0002
>0045
>0046
>
>

>use sales in 0 alias sales
>select sales
>mkey='003333'
>seek mkey order inv
>scan while inv=mkey
>    disp PK
>endscan
>use in sales
>

>
>result:
>-------
>0001
>0002
>
>
>thanks for the help