Collision within GameObject

Hey guys,
In my game I have it so when you push a button a cube appears in front of the player. I want to make it so that al the enemies within that cube take damage.

This is what I tryed doing.

Code (JavaScript):

1. var Attack : GameObject;
2. var Timer : float = 0.1;
3. var DestroyAttack = false;
4.  
5. function OnCollisionStay(collision: Collision) {
6.  
7.     if(collision.gameObject.tag == "Enemy"){
8.         var Enemy = collision.GetComponent(EnemyStats);
9.         Enemy.Health -= 250;
10.         DestroyAttack = true;
11.     }
12. }
13.  
14. function Update(){
15.  
16.     Timer -= Time.deltaTime;
17.    
18.     if(Timer < 0){
19.         DestroyAttack = true;
20.     }
21.  
22.     if(DestroyAttack == true){
23.         Destroy(Attack);
24.     }
25. }

I tryed get physics.overlapsphere to work but I have no clue what to do haha