Use the Expression option and the expression is isnull(controlname)

If you use the field name and value I think Is Null will also work

"Chegu Tom" wrote in message ...
isnull(ControlName)

"Anatoly Kurilin" wrote in message
...
Hi, what should I put in a text box "equal to" if I want a condition work
when the control value is equal to NULL?

Thanks in advance,
AK