My pup is 11 weeks old now and she is pretty good about house training...but its mostly if i am on top of her taking her out to pee. She does run to the front door when she needs to poop. So if I am watching her I know to let her out. But I'd like to train her to ring bells or do something so that I know (if I am in another room, or busy and not watching). So how do I go about training her to do this??