>thank you..
>
>But still I am wondering why a variable of type 'U' will give me a 'Variable Not Found' error when I run ISNULL() on it from the command window. But in the .exe, I do *not* get the 'Variable Not Found' error even though the variable that is being passed to the function has a type of 'U'.
>
>maybe there is something else going on here.

If the variable is declared (via a PRIVATE or LOCAL statement) in code, it is automatically initialized to .F.

Could that be the case here?