I was able to make this work for the following scenario... I wanted the redirect to go to one page if the user was creating a new item and another place if they were editing an existing item.
I used the IF function from the Inline Functions tab in combination with the "Is New Mode" option from the Common tab like this:
fn-If(Is New Mode,http://SharePointAddressForNewItems,http://SharePointAddressForEditItems)
Hope that helps!