Keeping cats from spraying?

The cats around here like to spray the trash cans under my car port, and it is getting pretty smelly now that the weather is getting warmer. 

I have heard that moth balls keep cats away, but they smell almost as much. 

Short of tying my dog up in the car port (he is a bit of a princess), does anyone know of any way to keep the cats away?

Clean the sprayed area well because if cats smell that an area has been sprayed before they will spray there.  We use an enzyme cleaner, also cats supposedly dislike the smell of citrus so if you used something citrus scented after cleaning it that might help as well. 

Maybe I'll pick up some of that orange oil cleaner, and put a big citronela candle out there.  Some of those candles put out quite a smell even when they aren't burning.

I also saw some motion detecting noise makers, that put off a high pitch sound that humans can't hear, but drives cats out of the area.  It sounds like they eat threw batteries though, and I don't have an easy way of getting power out there.

There is a contraption that is a motion detector squirt thing.  That should be fun.

I just heard that a product called "Bac Out" is great for this, and only costs about $6.  Might want to give it a shot.

paul wheaton wrote:
There is a contraption that is a motion detector squirt thing.  That should be fun.

Now that you mention that, I remember seeing a sprinkler with a motion detector on it for keeping birds out of your vegetable garden.