I recued a dog that is 8 years old 3 months or so ago and he is house broken. He has been having accedents, though not frequently. I dont think he would have these issues if he warned us that he needs to go out. He doesnt bark EVER. Not that its a bad thing, but it is since thats a way all other dogs ive owned let me know they needed to go out. Is there a way to "teach an old dog one last trick" and have him give me a sign he needs to go out. We walk him 3-4 times a day. 8:30 am, noon, 4:30, 9:00. Each walk is about 1 mile in distance, and he always goes number 1 and ever other time number 2. He litterally does not give a sign he needs to go out. Please help 