I'm having the same trouble with a neighbor's cat who keeps spraying my garage door. I've been using a mixture of liquid Downy and water in a spray bottle (no measurements - just lots of Downy diluted) and spraying around my door and shrubs and so far it is helping. Either that or the Downy smells so strong that I can't smell the cat urine anymore.

My garage door has that straight from the dryer fresh smell!

I was told it was a good cat repellent and I know Ripley took one sniff of the spray bottle and ran.

Also, the mixture diluted even more will help remove wallpaper from the wall - i just tried it last week and it worked wonderfully. Wonder what other uses I can find?!