Admob interstitial showing using listener

At present I can able to show interstitial ads of AdMob.
I have used following code for this.

        if (GUI.Button(new Rect(10, 300, 150, 50), "Load Interstitials"))
        {           
            interstitial.LoadAd(interstitialsRequest); 
        }

        if (GUI.Button(new Rect(10, 400, 150, 50), "Show Interstitials"))
        {       
            if (interstitial.IsLoaded())
            {
                interstitial.Show();
            }
        }

In this I want to attach listener for interstitial loading is complete. For this I have view all available source files but can’t able to figure out right listener method.

    void onAdLoaded()
    {
        print("Interstitial Ad Loaded");        
    }

    public void HandleAdLoaded(object sender)
    {
        print("HandleAdLoaded event received.");       
        // Handle the ad loaded event.
    }

I have used googleads-mobile-plugins for admob ads

At present ads are working perfectly but want to detect interstitial loading through listener.

Please help me in this and thanks for your time.

Something like this:

UnityAdListener listener;

listener.OnAddLoaded = HandleAdLoaded;

public void HandleAdLoaded(object sender)
{
    print("HandleAdLoaded event received.");       
    // Handle the ad loaded event.
}

Haven’t tested it so better check it out.