Mouse move question

Add a OnTriggerXXXXXX or OnColliderXXXXXX method and a boolean switch that is evaluated in Update that if false, will allow you to move and true will not allow you to move(update the transform.position).

Edit:

Something like:

 var depth = 10.0;
 var moveable = true;
 
 function Start ()
 {
      Screen.showCursor = false;
 }
  
 function Update ()
 {
         if (moveable)
         {
      var mousePos = Input.mousePosition;
      var wantedPos = Camera.main.ScreenToWorldPoint (Vector3 (mousePos.x, mousePos.y, depth));
      transform.position = wantedPos;
         }
 }
 
 function OnCollisionEnter(collision : Collision) 
 {
         // some check to see if you hit what you think.
         if (collision.gameObject.tag.Equals("wall"))
         {
             moveable = false;
         }
 }
 
 function OnCollisionExist(collision: Collision)
 {
         if (collision.gameObject.tag.Equals("wall"))
         {
             moveable = true;
         }
 }

But you have to adapt it to your code and game objects.