Collision based scoring system

Hello, I'm trying create a scoring system which involves collecting coins to increase the score and colliding with rocks, which decreases the score. I'm currently using this script:

     var score = 0;
 var scoreText = "Score: 0";
 var mySkin : GUISkin;
 
 function OnTriggerEnter( other : Collider ) {
     Debug.Log("OnTriggerEnter() was called");
     if (other.tag == "Coin") {
         Debug.Log("Other object is a coin");
         score += 1;
         scoreText = "Score: " + score;
         Debug.Log("Score is now " + score);
         Destroy(other.gameObject);
     }
 }
 
 function OnGUI () {
     GUI.skin = mySkin;
     GUI.Label (Rect (10, 10, 500, 200), scoreText.ToString()); }

The script works perfectly fine. However I'm unsure as to how to include a script which, on collision with a 'Rock', decreases the score. I've tried adding this to the original script, but to no avail:

 function OnTriggerEnter( other : Collider ) {
     Debug.Log("OnTriggerEnter() was called");
     if (other.tag == "Rock") {
         Debug.Log("Other object is a rock");
         score += -1;
         scoreText = "Score: " + score;
         Debug.Log("Score is now " + score);
     }
 }

Thank you for any answers or feedback. -Ben