I have two Westie puppies (about 7 months) who are doing very well in their house training. Currently they are placed in a play pen during the day when we are at work, free when we get home, and crated for bed (eventually we’d like them to be free 100%). The problem is when we are at home and they are free. When they need to go, they walk to the back door (which is where we go out to go potty), which is great! Except that if we don’t see them right away they end up peeing in the house. They don’t bark or come get us or anything. I’d be happy to let them out when they ask but we don’t always know they are at the back door. We tried jingle bells, but they scared them. What can I do to get them to verbalize their need?