onRollOver with nested movie clips

I’m having a hard time getting some nested movie clips to respond to an onRollOver event.

given:

_root.game_mc.gameVenueBtn_mc

game_mc will respond to onRollOver, but the gameVenueBtn_mc will not. If I change gameVenue_mc to a button, the hand cursor appears when it is over, but still no onRollOver event.

Can somebody please explain the simple rules about how nested movieClips identify the onRollOver?

Thanks for any help in advance!

:puzzled: