reload help

hello guys i have a question of my shoot script: how can i place a reload in my script. this is my script

 var shotsound:AudioClip;
 var shellPrefab : GameObject;
 var proyectilevelocity:int;
 var ammo:int;
 var fireRate = 1.0;
 private var nextfire = 0.0;
 function FixedUpdate () {
     if(Input.GetButton("Fire1") && Time.time>nextfire && ammo>0)
         ShotProyectile();
 }
 function ShotProyectile(){
         if(Time.time > nextfire)
         {
     var Grenade:GameObject = Instantiate(shellPrefab,transform.position,transform.rotation);
     Grenade.GetComponentInChildren(Rigidbody).velocity =transform.TransformDirection(Vector3(0,0,proyectilevelocity));
     //Physics.IgnoreCollision(shellPrefab.GetComponentInChildren(BoxCollider).collider,transform.parent.collider);
     ammo--;
     if(shotsound)
         audio.PlayOneShot(shotsound);
     Destroy(Grenade,10);
     nextfire = Time.time+fireRate;}
 }