Hi I know this is off topic for wood working but I know there are a lot of smart people with divisified back grounds.

I have a hot tub, the cover is relatively heavy. I want to design a lift system for the cover. I would like to have it controlled by a small compressor. I would like to be able to press a switch on the side and raise the cover about 4 ft then press the switch again to lower it back in place. I also want to do it cheap. Can someone tell me how to do this?