How can i run a login controller on all my pages?

[eluser]Unknown[/eluser]
How would i go about running my login code on all my pages?
I've the code for it done but in the CI structure i can't see how it fits.

Can i somehow run a controller like a masterController ? Simply put i want a window in
my layout-view to display "Your are logged in *user*" or "Please login" , for that to be determined it will obviously have to run the logincode on every postback kinda like this Codeigniter page where you've your login INFO always displayed on top.