Set borders to mouse follower?

Hey, I'm using a mouse follower in my game. My problem is that, if the cursor moves too off it goes through objects. But i only want it to move in a pre-set field, Help please

EDIT: The Code

 var depth = 10.0; 
 var speed = 1;
 
 function Start () 
 { 
      Screen.showCursor = false; 
 } 
 
 function Update () 
 { 
 if(transform.position.y<1||transform.position.y>-1||transform.position.x<1||transform.position.x>-1)
 {
 var mousePos = Input.mousePosition; 
 
      var wantedPos = Camera.main.ScreenToWorldPoint (Vector3 (mousePos.x, mousePos.y, depth)); 
      transform.position = wantedPos;      
 } 
 else
 {
 
 }
 }