Funnily enough, he is house trained. He sleeps inside at night (without belly band on) and always wees and poos outside. If he is doing a wee, he sill take himself out the dog door. However, the marking is entirely different. It is a few dribbles here and there, usually against the bottom of a door.
We are being vigilant in trying to catch him as he does it and then indicating "no". He is deaf and so is my other pug, so we have to be right there when he does it as he cannot hear us.
Belly band is on when he is inside (except over night) and he is taken out at 3 hourly intervals with belly band off to do a wee, so he doesn't wee in the belly band.