Unity menu by key with freeze to prevent menu blinking

using UnityEngine;
using System.Collections;

public class menuscript : MonoBehaviour {
	public bool menuopen;
	public float timeswitched=0f;
	public float menufreeze = 0.5f;
	public Rect windowRect = new Rect(100, 100, 80, 50);
	// Use this for initialization
	void Start () {
		menuopen = false;
	}
	
	// Update is called once per frame
	void Update () {
		if (Input.GetKey ("up")) {
			if (timeswitched + menufreeze < Time.time) {
				if (menuopen == false) {
					menuopen = true;
				} else {
					menuopen = false;
				}
				timeswitched = Time.time;
			}
		}
	}

	void OnGUI(){

		if (menuopen == true) {
			windowRect = GUI.Window (0, windowRect, DoMyWindow, "Game Time");
		}

	}

	void DoMyWindow(int windowID) {
		GUI.Label ( new Rect (45, 20, 45, 20), "Ya menu");


	}
}