What about getting him fixed. Most dogs that are intact run out the door in search of "booty".
Sorry, I was trying to make this funny! But seriously, they will run out and can sniff a bitch in heat miles away. I use to think neutering wouldn't really help Kaji. He was a year old, had been at his breeders house all along so I know he knows what a bitch in heat smells like, yet, neutering in combination with training and now I have an angel. It's a lot of work but I think it can be done. To further test my theory, Kaji and I went to visit BF, and his little sis's Maltese mix was in heat. Kaji and I were in the other room and he didn't care for her. He did want to play with her at first (Kaji loves to play!) but when I said no he just came to me and let her be. He really had no urge distracting him from what he already learned.