swa66 - 7:10 am on Jan 19, 2013 (gmt 0)

Sounds like you want to control where the back button in the browser goes to ?

That's commonly considered breaking the back button and should not be done.
I don't think you can do it on the server side of things, you can using client side scripts (javascript) AFAIK -more complex use of ajax sometimes needs to do this to keep the back button working properly.

What you can do relatively easy is to store server side for the given session what the user has been doing and keep a "state" for them, that should solve your need without changing the URLs.