Enemy AI won't take Damage

I have a simple combat script set up, but everytime the prefab hits the enemy the enemies health will not go down. I could use any help I’m at the verge of giving up on this I can’t figure it out.

public var path1 : Transform;
public var path2 : Transform;

public var enemySpeed : int = 6;

public var currentHealth : int = 1;
public var maxHealth : int  = 1;

private var target : Transform;
private var controller : CharacterController;

function Start () : void 
{
	SetTarget(path1);
	controller = GetComponent(CharacterController);
	currentHealth = maxHealth; 
	gameObject.renderer.material.color = Color.red;
}

function SetTarget(newTarget : Transform) : void
{
	target = newTarget;

}

function Update () : void
{
	var lookAtPosition : Vector3 = new Vector3 (target.position.x, this.transform.position.y, target.position.z);
	transform.LookAt(lookAtPosition);
	controller.SimpleMove(transform.forward*enemySpeed);

}

function OnTriggerEnter (node : Collider) : void
{
	if (node.transform == target)
	{
		if (target == path1)

			SetTarget(path2);
				
		else if (target == path2)
			SetTarget(path1);

}		
}

function ModifyHealth (change : int) : void 
{
{
	currentHealth += change;
	if (currentHealth > maxHealth)
		currentHealth = maxHealth;
	else if (currentHealth <= 0)
			Destroy(this.gameObject);
		

}	
}



this is the bullet script

var shot : GameObject;
function Start()
{
}

function OnCollisionEnter(info : Collision) : void {
	if(info.collider.tag == "Enemy"){
		info.collider.SendMessageUpwards("ModifyHealth", -1);
	}
}
function Update () {
if(Input.GetButtonDown("Fire1"))
{
var porjectile = Instantiate(shot, transform.position, Quaternion.identity);
porjectile.rigidbody.AddForce(transform.forward * 1500);
}
}

Perhaps try using info.gameObject.SendMessageUpwards() instead of info.collider.SendMessageUpwards(). That should ensure that the message reaches all scripts attached to the enemy game object. You will also need to use if(info.gameObject.tag == “Enemy”) instead of what you have now, because tag is not a member of collider.