G.W.
I'm a little behind the times here, but I have the same problem and I am glad I found this post. It reminds me of a way I kept my cats from going where I didn't want them - such as getting up on furniture. I will have to try the mothballs if this old trick doesn't work: I soaked cotton balls in nail polish remover - the cats hated the smell - and placed them around the areas I didn't want them to go. Worked like a charm. After the first few smells they stopped going that way. Now when doing this, I don't recommend placing the balls directly on the carpet or furniture, due to the nature of nail polish remover, but on a little tray or some paper.
You'd be surprised how long that smell stays on those cotton balls, but they may replacement after 3 weeks or so.