I've trained mine with poochie bells, too. I have them at both doors. Stitches29 also uses them.
When I first put them up, I just took her little front paws in my hands and we rang it together until she learned and I would ask her at the same time if she wanted to go potty (or whatever you say). Of course, mine looooooves to go outside, so she'll ring it to go outside and to potty. At any rate, she has been fully house broken for sometime now.
