Making A GUI.Box visible or invisible using a keyboard keystroke

Unity Engine
1

How would you use a keystroke to make a GUI.Box visible or invisible. This is what I have now.

void OnGUI() {
GUI.Label(new Rect(screenPosition.x - 36, screenPosition.y - 35, Screen.width / 8, 7), “Health”);
GUI.Box(new Rect(screenPosition.x - 36, screenPosition.y - 35, healthBarLength, 7), “Health”);
if(Input.GetKeyUp(KeyCode.U))
{
GUI.enabled = false;
}
}

the GUI.enabled = false does not do anything though

2

would this work:

How to Hide GUI Box Once Clicked?
http://answers.unity3d.com/questions/25142/how-to-hide-gui-box-once-clicked

3 
boolean showWindows = false;
void OnGUI() {
    if(showWindows)
        GUI.Label(new Rect(screenPosition.x - 36, screenPosition.y - 35, Screen.width / 8, 7), "Health");
        GUI.Box(new Rect(screenPosition.x - 36, screenPosition.y - 35, healthBarLength, 7), "Health");
    }
}

void FixedUpdate() {
    if(Input.GetKeyUp(KeyCode.U))
    {
        if(showWindows)
            showWindows = false;
        else
            showWindows = true;
    }
}
4

Thanks so much, appels!