Extend Custom Controller?

[eluser]RandyCram[/eluser]
I am working on a rather large project and It is going to have admin/moderators/members and what not so I want to create a controller (ex: admin_controller.php) that I can extend to do the checking if person is admin or not. I know that to load controllers you need to autoload them or something like that but i did a require_once in the MY_Controller.php but no matter how i get it to work, the actual controller that does the loading of view's etc.. basically ignores the rules set in the admin_controller.php.

Any thoughts??