Form rule to hide panel if a text box has a value

Good evening,

I'm trying to hide a panel if a text box contains a value (any value) and I can only get the opposite to happen.

I have a text field called SRPNo. If the field has not value the panel named DivAuth needs to be completed. If a value is entered into the SRPNo field the DivAuth panel needs to be hidden.

The only thing I can make work is isNullOrEmpty(SRPNo) however this gives me the opposite of what I want. One site I found referened using SPRNo!=" which is supposed to hide the panel if the field is not blank, however when I add this rule and test it the entire form does not show up.

Any ideas would be appreciated.

Thanks

Andrew