StarFighter game script Help

Unity Engine
1

my StarFighter game is almost finished but i’m hung up on the is one script my Radar script it needs to put a marker over the AlienShips not every object in the scene, I need the script to put a marker above the object with the tag AI. How would I write that in this script?

here is the Game if you would like to see how it works.
press #1 and left click to fire a black hole. press #2 And Left click to fire a Rocket or Right click To fire a WormHole.
http://dl.dropbox.com/u/21120930/StarFighter/WebPlayer/WebPlayer.html

var AIE : GameObject;

function OnTriggerEnter (col : Collider) {

//var AlienShip =col.GameObject.Tag==("AI");

	

var position: Vector3 = Vector3(Random.Range(-150.0, 150.0), 0, Random.Range(-150.0, 150.0));

    Instantiate(AIE, position, Random.rotation);	

	

var Label=GameObject.FindGameObjectWithTag("Label");

Label.GetComponent(DistensLabel).Target=col.gameObject.transform;

Label.GetComponent(ObjectLabel).target=col.gameObject.transform;



Label.tag="Untagged";



	

}



var x = 0;

var y = 10;

var z = 0;





function Update () {

transform.Rotate(x, y, z*Time.deltaTime);

}
2 
GameObject[] ais = GameObject.FindGameObjectsWithTag("AI");
if(0 == ais.Length)
	foreach (GameObject go in ais)

find is always slow so you should avoid doing this every update. do it in the beginning and when ai objects are added or destroyed and cache the result somewhere.