Change mouse sensitivity when an input is held?

I've been trying to get a script written to make the camera speed change when an input is held. Here's a script I wrote already that changes player speed when an input is held. Here's that script if it helps...

Code (JavaScript):

1. var walkSpeed: float = 7; // regular speed
2. var aimSpeed: float = 3.5; // run speed
3. private var chMotor: CharacterMotor;
4. function Start(){
5.      chMotor = GetComponent(CharacterMotor);
6.      var ch:CharacterController = GetComponent(CharacterController);
7. }
8. function Update(){
9.      var speed = walkSpeed;
10.      if Input.GetButton("Aim")){
11.          speed = aimSpeed;
12.       }
13.       chMotor.movement.maxForwardSpeed = speed; // set max speed
14.       chMotor.movement.maxBackwardsSpeed = speed; // set max speed
15.       chMotor.movement.maxSidewaysSpeed = speed; // set max speed
16. }