[Zope] nav trees

I'm using a tree tag for a navagation system which you can see at http://www.3e.org/elena/ . The problem I'm having is that if you click on the title of a folder (instead of on the +/- like you're supposed to), you end up with another copy of the site nested in the target frame. How would I make it so the folder names would *not* be links? Daniel Drucker