how to make AI reduce PlayerHealth ??

Can anyone give me a script to make the A.I reduce the Player's Health??

this is my health script

PlayerHealth JS script

 static var curHealth : int = 100;
 static var maxHealth : int = 100;
 
 var healthtext : GUIText;
 
 static var curXp : int = 0;
 static var maxXp : int = 500;
 
 var xptext : GUIText;
 
 var level :int = 1;
 
 
 static var minAttack : int = 10;
 static var maxAttack : int = 50;
 
 static var attackPower : int = 2;
 
 
 
 function Start () {
 
 
 healthRegen();
 
 }
 
 
 
 
 
 function Update () {
 
 
 healthtext.text = curHealth + " / " + maxHealth;
 
 xptext.text = "Level " + level + " xp " + curXp + " / " +maxXp;
 
 
 if(curXp == maxXp) {
 
 
 levelUpSystem();
 
 
 }
 
 
 
 
 if(curHealth < 0 ) {
 
 curHealth = 0;
 
 
 }
 
 
 if(curHealth > maxHealth) {
 
 
 curHealth = maxHealth;
 
 
 }
 
 
 
 if(Input.GetKeyDown("e")) {
 
 curHealth -= 10;
 
 }
 
 if(Input.GetKeyDown("r")) {
 
 curXp += 10;
 
 }
 
 
 
 
 }
 
 
 
 
 function healthRegen () {
 
 
 for(i=1;i>0;i++) {
 
 
 
 yield WaitForSeconds(0.5);
 
 if(curHealth < maxHealth) {
 
 curHealth++;
 
 }
 
 
 }
 
 
 }
 
 
 function levelUpSystem () {
 
 
 curXp = 0;
 maxXp = maxXp + 50;
 level++;
 
 maxHealth += 50;
 
 
 
 
 
 }

========================================================================================= //

I try with This script ,BUT not work

 var cube : GameObject;
 
 function Awake()
 {
 cube = gameObject.FindWithTag("Player");
 }
 
 function OnCollisionEnter(hit : Collision)
 {
 if(hit.gameObject.tag == "cube")
 PlayerHealth.curHealth -= 20;
 }

========================================================================================= //

Please Assist :)