Oh Kitty Cat, Oh Kitty Cat....

Today was a very dull day here at the beach.  Overcast, rain off and on and wind.... yuck!  Who would want to sneak into our backyard during a day like this???  Well no person better be in our backyard period, but I look outside and find a cat jump over our fence, walk it's little behind over to my son's sandbox, dig a small hole and then drop it's little butt right in the hole and relieve itself.  At this point I'm mad, really cat?  My son plays there and this is MY yard and I hate cats so GET OUT!  I start banging on the window like that will do anything and the nasty little thing just looks at me with it's glass eyes.... like it is saying, "Yeah I peed, whatcha gonna do about it!"  Rrrrrr, I'm so mad!  How do I get a cat out of my backyard that is surrounded by other houses all the way around? or How do I get a cat out of the sandbox without having a proper cover?  Jamie and I kinda "created" a sandbox under the swing set.  It isn't really a sandbox so there is no cover, except a blow up kiddie pool that I throw over the top to keep rain and leaves out, but it obviously don't work for cats.  I would really like some feedback people!!!!  Thanks! :)