Help with understanding and modifying a camera script (JavaScript)

So, I'm making a game, but have very little experience with UnityScript, although I have learned Java and JavaScript. One part of the game I am having trouble with is the script for camera movement. I'm currently using the Camera Orbit script that came with unity, but want to modify it so that

1: It only runs when the Right mouse button is pushed down, and

2: The scroll wheel allows the player to zoom in and out on the object.

Well, I've looked into both of these things ALL OVER the internet, but cannot find the help that I am looking for. So, heres the code:

 var target : Transform;
 var distance = 10.0;
 
 var xSpeed = 250.0;
 var ySpeed = 120.0;
 
 var yMinLimit = -20;
 var yMaxLimit = 80;
 
 private var x = 0.0;
 private var y = 0.0;
 
 @script AddComponentMenu("Camera-Control/Mouse Orbit")
 
 function Zoom () {
     if (Input.GetAxis("Mouse ScrollWheel") == -1 && distance < 125) {
             distance += 5;
     }
     if (Input.GetAxis("Mouse ScrollWheel") == 1 && distance > 25) {
             distance -= 5;
     }
 }
 
 function Start () {
     var angles = transform.eulerAngles;
     x = angles.y;
     y = angles.x;
 
     // Make the rigid body not change rotation
        if (rigidbody)
         rigidbody.freezeRotation = true;
 }
 
 function LateUpdate () {
     Zoom();
     if (target) {        
         x += Input.GetAxis("Mouse X") * xSpeed * 0.02;
         y -= Input.GetAxis("Mouse Y") * ySpeed * 0.02;
          
          y = ClampAngle(y, yMinLimit, yMaxLimit);
                 
         var rotation = Quaternion.Euler(y, x, 0);
         var position = rotation * Vector3(0.0, 0.0, -distance) + target.position;
         
         transform.rotation = rotation;
         transform.position = position;
     }
 }
 
 static function ClampAngle (angle : float, min : float, max : float) {
     if (angle < -360)
         angle += 360;
     if (angle > 360)
         angle -= 360;
     return Mathf.Clamp (angle, min, max);
 }

The zoom function was my poor attempt at solving my problem, but it didn't work, even if it did compile. I never implemented the RightMouseDown script because I had no idea how to. Also, one other thing. If you could also help me make sense of what all this means, and anything that you add or change does, it would be very helpful, as I only have a VERY basic idea of how it works.

Thanks!