Hide Visibility of text box if not string1 or string2

This should be an easy fix but can't get it to work. Have a field called "Roommate" and I only want to value of this text box to show when string1="international" or string1="StateSide". So far I have tried to expression below under text box properties-Visibility- Show or Hide based on expression.  No luck

=iif (Fields!String1.Value <> "International" or

  Fields!String1.Value <>"StateSide",true,false)

thanks

kam