If your schedule permits I would recommend ONLY outside as a place to "do business." Dogs like to keep it simple. To help in establishing the concept of "outside" I would recommend something like this (see link below). We have been at it almost 2 weeks with our 14 week old and she already knows what the bells are for, though she sometimes has to be encouraged to use them. She definitely knows what "outside" means.
http://www.poochie-pets.net/