gaze and pick with a delay

Hi
After watching a few tutorials, I have managed to implement gaze and pick and now i need to include a delay so the player doesn't mistakenly change scene when their gaze just passes over the button. I have tried following a few tutorials but I can't get the delay to be dependent on the focus remaining on the button. This is what I have in my script:

using UnityEngine;
using UnityEngine.SceneManagement;

public class LoadLevelAfterTime : MonoBehaviour
{
[SerializeField]
private float DelayBeforeLoading = 10f;
[SerializeField]
private string scenenameload;
private float timeElapsed;

public void Update()
{
timeElapsed += Time.deltaTime;
if (timeElapsed > DelayBeforeLoading)
SceneManager.LoadScene(scenenameload);
}

}

would appreciate either a link to documentation or better yet a tutorial on how to implement this or if it is an easy fix help with my script.

thanks v much
Nick