Does the IIf function work differently in queries from the way it works in 
reports?

For example, this works in a query: 

lastName: IIf([Last]="Smith",Null,([Last]))

(I can hid the last name "Smith" in the lastName field.)

However, I cannot use the same IIf as a control source in a report.  It 
generates a circular reference error message.

= IIf([Last]="Smith",Null,([Last]))

(If the name is not "Smith", then print it.)

Is this just how IIf works?