How do you make object stop after traveling a certain distance by pressing a key?

I want to make my object moving up and down by pressing key and stop, so that the object won't go out of the camera.

 public bool up;

 void Update()
 {
     if (Input.GetKeyDown(KeyCode.Space))
     {
         up = !up;
         if (up)
         {
             //make object transform up and stop after certin distance
         }
         else
         {
             //make object transform down and if touch the ground, stop
         }
     }
 }