how to asign new value oncollisionEnter

Hi I m trying to create some AI system with RAIN AI.

for this i need to change values of different variables

i want to change value after detecting collision in this case. i want to change health from

health of 100f to health of 5000f

using UnityEngine;
using System.Collections;
using RAIN.Core;

public class Health : MonoBehaviour {
public float nastroj=10f;
public float health = 100f;
private AIRig aiRig =null;

// Use this for initialization
void Start () {
	aiRig = gameObject.GetComponentInChildren<AIRig> ();
}

// Update is called once per frame
void Update () {
	aiRig.AI.WorkingMemory.SetItem ("health", health);
	aiRig.AI.WorkingMemory.SetItem ("nastroj", nastroj);
}	
void OnCollisionEnter(Collision collision)
{
	aiRig.AI.WorkingMemory.SetItem ("health", health=2000f);
	aiRig.AI.WorkingMemory.SetItem ("nastroj", nastroj);
	---->????health=500f;
           ---->???? return health;

}

}

On____Enter (Type val) {
if(val.tag = “Player”)
health = 5000
}