LOL - we successfully trained ours to ring the bells when they needed to go outside to potty. Unfortunately, they LOVE going outside, and we don't have a fenced yard to let them run around by themselves in, so we have to go with them each time. They were ringing that thing every two minutes! We'd go out, play a while, come back in, and they were ringing it again in two minutes.

We eventually took the bells away and went to using piddle pads indoors. Now going outside is a special treat.