Hit Marker

Ok here is my damage receiver script

 var hitPoints = 100.0;
 var detonationDelay = 0.0;
 var explosion : Transform;
 var deadReplacement : Rigidbody;
 
 function ApplyDamage (damage : float) {
     // We already have less than 0 hitpoints, maybe we got killed already?
     if (hitPoints <= 0.0)
         return;
         
     hitPoints -= damage;
     if (hitPoints <= 0.0) {
         // Start emitting particles
         var emitter : ParticleEmitter = GetComponentInChildren(ParticleEmitter);
         if (emitter)
             emitter.emit = true;
 
         Invoke("DelayedDetonate", detonationDelay);
     }
 }
 
 function DelayedDetonate () {
     BroadcastMessage ("Detonate");
 }
 
 function Detonate () {
     // Destroy ourselves
     Destroy(gameObject);
 
     // Create the explosion
     if (explosion)
         Instantiate (explosion, transform.position, transform.rotation);
 
     // If we have a dead barrel then replace ourselves with it!
     if (deadReplacement) {
         var dead : Rigidbody = Instantiate(deadReplacement, transform.position, transform.rotation);
 
         // For better effect we assign the same velocity to the exploded barrel
         dead.rigidbody.velocity = rigidbody.velocity;
         dead.angularVelocity = rigidbody.angularVelocity;
     }
     
     // If there is a particle emitter stop emitting and detach so it doesnt get destroyed
     // right away
     var emitter : ParticleEmitter = GetComponentInChildren(ParticleEmitter);
     if (emitter) {
         emitter.emit = false;
         emitter.transform.parent = null;
     }
 }
 
 // We require the barrel to be a rigidbody, so that it can do nice physics
 @script RequireComponent (Rigidbody)

And here is my damager sender script

 var damage : float;
 
 function OnCollisionEnter (other : Collision){
          // Tell the object you hit that it was damaged
          other.collider.gameObject.SendMessage("ApplyDamage", damage, SendMessageOptions.DontRequireReceiver);
 }

Now i need a script to attach to a gui, so the gui only pops up when you sending damage.