Hi June, I do not have cats, however I have seen covered, ferret litter pans that would appear to be too small for a cat to fit into. I believe I saw them at the Ferret Store. This would probably discourage your cats from trying to use your ferrets boxes. It will mean buying new litter boxes, but it might be worth it if you are really have that hard of a time with it. But you could just use the boxes you have now as clean reserves for when you change the ones in their cage. Good luck! Jenna [Posted in FML issue 2929]