Getting a div to slide back after choosing another...

Getting a div to slide back after choosing another...

I'm putting together a 'form chooser' that slides a form (div) from behind the menu when clicking a link. That's all fine and good. But upon choosing another, the form simply disappears and the new one slides from behind the menu:

Here's the page...

What I would like to have happen is when you choose another form to appear, the last one slides behind the menu as/after the next one appears.