I've never had a cat that didn't know how to use the litter box. All I can think of is to maybe try using some Cat Attract Litter by Dr. Elsey. It's supposed to help cats that won't use the litter box. You can buy it at Petsmart or order it online. I don't know if any other other pet stores carry it yet but I think I saw some of Dr. Elsey's cat litter's in a Petco before. Here's a link about it: http://www.petsmart.com/product/inde...ductId=2751734. Good luck.