I think this has come up once before. Is there any way to put the litter box in a room so that you could put a baby gate in front of the room?
This is the set-up I have. A spare bedroom is the cats' room. The 2 litter boxes are in one corner, and the cats' food bowls are in another corner. There is a baby gate in front of the door, so the cats can easily jump over, and the dogs can't.