>>You can add
>>
>>=messagebox(vartype(aaa))
>>
>>in the form's Init.
>
>I see... Thanks for your help. It's a public variable, as evidenced by DISPLAY MEMORY. I didn't know that the variables were created automagically, and the help topic for "ControlSource" doesn't mention it.

Hilmar,

some process needs to create the variable.

Trace it down:

on app start

CLEAR ALL
DEBUG
SUSPEND

Now debugger should be open, no variable should exist
in watch window add type('aaa') It should show 'U'
Click the left border next to TYPE to set a breakpoint
run the app. As soon as the variable is created, the debugger should stop.

Update:

if this creates with the IDE,

start vfp.exe with an additional fpw config file, the config should start a prg what itself does the lines above.