Removing A Component From An Instantiated Prefab After X More Are Instantiated

I am trying to remove a rigidbody from an instantiated object after x more are instantiated after it.Here is my script :

public var cube : Transform;
public var cubeclone : Transform;

public var counter;

 function Update () { 

    if (Input.GetButtonDown("Fire1")){
        var count = counter;

     cubeclone = Instantiate (cube, Vector3 (transform.position.x, transform.position.y, 0), Quaternion.identity);

        transform.position.y += 0.5;
        counter++;

     if (counter == count + 4) {
       Destroy(cubeclone.rigidbody);}

                        }

        }

Also the script only instantiates a cube if counter++ is at the bottom like it is now. Any help would be appreciated.

I think this should work

if (counter == count + 4){
    Destroy (GetComponent (Rigidbody));
}