I want something a little different from that though.
I have a drop down with just names. I want to send the notification email to the person that was selected, but their email address isn't an option on the drop down.
I made the drop down with names a variable in a calculated field and assigned the email address to the appropriate person in the Variable Value section. When I go to the hidden field, the variables aren't an option.
Have a look at this screencast: http://screencast.com/t/bKC7NuwjLvIw
I didn't save the changes, because I wasn't quite sure what you were wanting to accomplish with your if statement in the calc box, but you should be able to get the behavior you want by placing AMmail in the calc box.