Want to make a following enemy freeze when visible by main camera

Hi, I'm creating a game, and I have an enemy that at the moment follows my character (main camera) but I want it to stop moving (freeze) when it is visible by the main camera, I also want it to start playing a sound when the enemy is close to my character. I know similar questions have been answered on this forum, but none in a very straight forward way, because I am new to this, so my knowledge is very thin. This is my entire code for the enemy at this point:

var rotationSpeed = 3; //speed of turning

var myTransform : Transform; //current transform data of this enemy var target : Transform; //the enemy's target var moveSpeed = 5;

function Awake() { myTransform = transform; //cache transform data for easy access/preformance }

function Start() { target = GameObject.FindWithTag("Player").transform; //target the player

}

function Update () { //rotate to look at the player myTransform.rotation = Quaternion.Slerp(myTransform.rotation, Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed*Time.deltaTime);

 //move towards the player
 myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
   
   
 }