I'm looking for a bit of advice please - my 3 year old Cairn terrier is totally housetrained, and has been since puppyhood, but has recently started weeing in the house....specifically at the kitchen door. He mainly stays in the kitchen/family room as that is where we all hang out, or comes through to the living room with us in the evening. He is not allowed upstairs as that is the cats territory! However he has developed this habit of weeing against the kitchen door whenever he hears the cat passing in the hall on her way in or out, and for the last week has been doing it every time the front doorbell rings. I'm assuming it's a territorial thing, but how do I get him to stop?