I have a cheap octave stomp box pedal that I dont use any more.
I also have an amp with no footswitch.
Is it possible to rewire the pedal and make a footswitch out of it?

Thanks for any help
Probably not. Just go to the 'Shack and get an SPST push-button switch, a cord with a 1/4" stereo plug, and their smallest enclosure. Total price is prolly about 8 bucks. I did this and it works just great. I think I have a pic in my profile.

Buuuut, if the pedal has an actual mechanical switch, then yes. Just strip out everything except the switch and solder a cord with a 1/4" plug to it.