Multitouch and collision for android

Hi!

I am making my first android game for android and I'm new to unity. I know the basics however.

I am trying to make 2 - 4 different blocks move on the y-axis by touch and dragging. They have to move independently by multitouch. I've got the code for moving them done, however I need to limit them so that the blocks can't go out of the cameras view. Multitouch isn't working either.

(to seperate which object is being touced I use tags "LeftBlock" and "RightBlock")

Here's the code for the blocks:

 var speed : float = 0.01;
             
             function Update () {
                 if (Input.touchCount > 0 && 
                   Input.GetTouch(0).phase == TouchPhase.Moved) {
                   {
                   var ray = Camera.main.ScreenPointToRay (Input.GetTouch(0).position);
                   var hit : RaycastHit;
                if (Physics.Raycast (ray, hit) && hit.transform.gameObject.tag == "LeftBlock") 
               {
                 
                     // Get movement of the finger since last frame
                     var touchDeltaPosition:Vector2 = Input.GetTouch(0).deltaPosition;
                     
                     // Move object across XY plane
                     transform.Translate (0, 
                                 touchDeltaPosition.y * speed, 0);
                         }
                 }
             }
             
         }
 

I would be very grateful for a quick reply.

Thanks,

Adam