House-breaking a Yorkie

Question
My wife has a small, male Yorkshire Terrier who is about 5 years old. He was just under a year old when we got him. Until last February, he was left alone in the house while my wife worked and was never completely housebroken. I retired and am now here and we go for walks which he seems to love. If for some reason I do not walk him when he needs to go, he will relieve himself in the house. Is there a way to retrain a dog of his age to let us know when he needs to go and to discourage him from going in the house? He is probably the sweetest, most loving dog I have ever known. It might be relevant for you to know that we had him neutered about a month ago, but this does not seem to have affected this behavior.

Answer
Hi,
 Sorry it has taken me so long to answer.  I have been out of town.  You need to get a CRATE!  It isn't cruel at all to crate them.  You have to think of it as being a 2 year old forever.  You wouldn't let your toddler run around the house unsupervised.  You would put them in a crib or paypen of some sorts.  
 If the dog is used to being walked at a normal hour then you must stick to it.  He is on a schedule.  They are creatures of schedules.  They like being on time.  
 If you have any questions feel free to email me.
Thanks Tammy.