I have a six month old English Shepherd/Poodle cross. He is house trained on the first floor of the house. Goes to the do and barks when he needs to go. However, when he is on the second floor of the house he invariably relieves himself. How do I get him to understand that upstairs is also part of his space and not to eliminate there? I have shown him the door upstairs to go out and taken him out of it, but that does not seem to be computing in his mind.