You could try to use FSIZE() function

IF FSIZE("source_in_question") = 0
* this in not a field

>I've been looking for a VFP function or a UDF that will allow me to determine if an object's control source refers to either a column in a cursor/table or to a memory variable. If it refers to a column I need to do a REPLACE command to update the column. If it refers to a memory variable I need to replace the value in the variable. Something like this is what I'm looking for:
>
> IF OBJTYPE(Object.ControlSource) = 'C'
> REPLACE (Object.ControlSource) WITH ltNewDateTime
> ELSE
> STORE ltNewDateTime TO (Object.ControlSource)
> ENDIF
>
>Thanks!!!
>Jim