[ImSoYesterday]

Which part would that be?

Get a 1-positional switch and wire it to the motor. The motor will activate when the switch is toggled and the second you take pressure off the switch will disengage and the motor will stop. You can use a standard 1 position switch with a long attachment on it to eliminate the stopper, just make sure it is mounted properly so you get NO play in that switch. Make sure to get a fuse in your box or just a standard fuse holder, you shouldn't need more than a 1 amp fuse but go with 5 to be safe. I did the math. with a motor you will need, should run off of 9v or so. go to radio shack and pick up a resistor. Snow day today, I don't have my notes, but I will find out more about it tomorrow, I'm sure if I played with it at school tomorrow I could draw up a schimatic for you.