Well, in this case you should code yourself, I think. Larry gave you good advise. You can redirect SET to the file and then search there for "USERNAME".
I did not try it myself, but it looks possible to create VFP exe file where sys(0) is used to identify username, and run it from Dos prompt.

>>Are you able to run net user?
>I tried issuing NET USER from a DOS window and USER is an invalid option. I >can run NET USE for what it's worth.