Servo question

[Micah Chetrit]

Hello,
This is not about FRC, just a project, and CD is my go to place for electronics and such.

I am not an expert on circuit theory or servos, and I am trying to help a friend on a project. He wants it cheep (so no arduinos), and he needs it so when you flip a switch, the servo goes from full forwards, and when you switch it again, it goes full backwards (if it can only go to center, that's fine too). Is there an easy way to do this? I would think that putting the switch inline with the white signal wire would do the trick for center to one end. Can I get some expert advice?
Thanks for your time,
Micah