Make my gameobject bounce

i have a die(dice) and a button

after clicking the button, i want my gameobject to bounce and roll in a random way like playing a real dice game

 here is my button code, i have a spawnpoint where the die will spawn
     
     var SpawnPoint : GameObject;
     
     function OnGUI() 
     {
         if(GUI.Button(Rect(640,40,150,50), "ROLL DIE")) 
         {
             SpawnPoint.transform.position = transform.position;
         }
     }


 here is my bounce code:
 *my function start is only for hiding my gameobject under the terrain
 *my real problem here is that, the die do crazy bounces like teleporting
  or what so ever crazy stuff after colliding to my background
  what should i do to my codes...help me pls :(
 
 var direction = Vector3(2, 1, 0);
 
 function Start()
 {
     transform.position.y = -10;
 }
 
 function Update()
 {
      transform.Translate(direction * Time.deltaTime); 
 }
 
 function OnCollisionEnter(theCollision : Collision)
 {
 
     if(theCollision.gameObject.name == "BackGround")
     {
         direction.y *= 10;
     }
 }

Please excuse my poor/bad English =)