If health = 0, show a GUI.button C#

I want to know the lines of script to add on in order that when the player health = 0 or is destroyed, a GUIbutton is shown. I have tried to do this but it does not work. Here are the exerpts from my script-
Thanks,

void Update(){

    health += Input.GetAxisRaw("Horizontal");
    if (health < 0){ 
		health = 0;
		destroy = true;
		Destroy();

}

void Destroy(){

	if(GUI.Button(new Rect(100, 100, 100, 100),"Level Complete")){
			Application.LoadLevel(1);
		}

The code would be the same in both languages. Just paste your js code into your c# class. Except instead of function OnGUI() it’s void OnGUI()

Did this and worked (did not use Destroy()):

void OnGUI()
{

if(destroy == true){

GUI.Box(new Rect(400,150,500,300), “Level Complete!”);

if(GUI.Button(new Rect(100,100,80,80),“Next level”)){

Application.LoadLevel(1);
}
}