I TOO have had a cat problem.......) has decided that he likes the carpet behind the couch in the den............as his private litter box]
well my DD has problems with her cats[6] with scratching the furniture, she put heavy duty DBLE stick tape on the spots and the kitties do not like getting stuck and leave the area alone .. You might like to try this on the carpet area, after cleaning and de odor izing the best you can.. good luck
Katie