Session expire and redirect to another page

Hi All, I have one problem in my web site, I need to redirect my application when there is no action for three minutes. I used session timed out period in the web config file. But When I am working with my content page its not working, because my content page is inside a update panel which is in the master page, so the content page not getting refresh at all, so the session expires.
I used javascripts and some other c# codes but still I'm having problem on this. Let me have some good solution....
I'm using ajax, So if there is any ajax solutions, I can use it.
Thanks in advance.