menu in a custom control on a master page help

[Tommy]

I am working on a site that uses a menu control. Because I need more than
one master page for different looks I put the common controls in webcontrols
and use them in the master pages to maintain the same look of the menu, etc.

My problem is in my app i need to access that menu control and remove or add
a few things based on the users security settings.

I tried me.FindControl("mnuMain") and it always comes back as Nothing.

How can I find a reference to that control so that I can manipulate it?

Thanks in advance.

Tommy