You have to pass output parameters by reference

SQLExec(nsql,[Exec dbo.UpdateCreditorBatchNo 'D',?@MyVar],'Temp')

>

>MyVar = Space(36)
>SQLExec(nsql,[Exec dbo.UpdateCreditorBatchNo 'D',?MyVar Output],'Temp')
>

>
>The Sp executes just fine in QA and returns a GUID.
>
>It also executes with a return value of 1 in VFP, but returns zilch.
>
>So, what am I doing wrong?
>