Android :: Closing Several Activities Simultaneously

In my application you can navigate through several Activities until the Activity stack is quite deep.

We'd like a button on every Activity that will take you straight back to the main menu - i.e. pop all Activities from the stack except the first one.

I've put the button in a View that I can easily put on every Activity in the application, but I can't figure out how to close several Activities in one fell swoop.

(If possible, it would be good if the View could work out how many Activities to close by itself - i.e. detect how deep on the stack its own Activity is.)