random level loader?

i already have a game set up and ready to be played, but i have one problem.

the character starts in a small room, and when they exit through a door, it should take them to 1 of 12 different level outcomes. i have the level loading script, but i'm not sure how to splice the random generator into the level loader. anyone know how?

 function Start() {
 number = Random.Range(1,12);
 }
 
 function OnCollisionEnter (collision : Collision) {
     if (collision.gameObject.name=="Player")
         Start();
         
         Application.loadLevel(1);
 }