Have a great idea, just don't know how to make it

[Erebus]

I am usually the one that can make anything, but I am stumped. I want to make a prop that will throw a fake rat at the TOT, and then come back and reset it's self so I don't have to walk over there everytime to reset it. I have a fence that I make every stay behind, and plan on attaching a fishing string (or something similar) so that it won't actually hit them, just come close and scare them. I plan on making the string long enough to make it to the fence, but not over, and some how have it attached to a motor or something and it will bring it back and reset its self. So far, I think I can use a pneumatic cylinder to lauch the rat (size and bore not determined yet), and I am thinking some how use a fishing reel to bring the rat back. I just don't now how to make it all work. I want a flat surface a little larger than the rat so be pulled on, the whole surface will move to throw the rat. That part I think I can make easily with a cylinder, but how to get the reel to release and everything, I am stumped. Any one have any idea?