MS ACCESS Report Problem

I’m trying to change the VISIBLE property of a TextBox by making expression.

textbox: desc1 */ I use IIF Func to check if
empty or not
textbox: text1 */ if not empty, make visible else
make invisible

the exact expression that I made was

IIF(Desc1 <> null, text1.visible = true, text1.visible = false)

Anybody can tell me what am i doing wrong?

Thanks.