I know. Sounds like a waste but..... fill a spray bottle with cheap vodka, spray the area well and let dry. While waiting for the area to dry, loosely cover with foil. (Don't chew me out for having foil please but the cats won't walk on it) Spray again once it's dry and again cover with the foil. That should do it. If you ever get a "whiff" of urine, just douse it with the vodka again and leave the foil in place until the cats lose interest. Hope it helps you as much as it's helped me.