I am sorry you are having trouble with your cats. I am a staunch cat lover, and I sure do hate to hear when there is troulbe. It has been my experience that once the cats does this, it doesn't stop. I had to replace carpet in one room that my cat found a spot to pee on. The cat wound up leaving at he did go to the new carpet also. I had tried putting a litter box right over the spot. I was also told to put fresh boxes on any suspected area and treat with a solution. I think the solutions do not penetrate to the sub surface, therefor the cat can still smell. Try multipal boxes set over a treated spot in your living area. There are also outdoor pens you can purchase through speciality catalogs. These are enclosures so they can have fun outside, and of course do their business in the box Outside. Cats are subborn critters, and I really hope you find a solution. ginnie