How to get Wifi wifi strength realtime in Windows Phone 8.1

Hi,

I get wireless signal by this code below:

var internetConnection = NetworkInformation.GetInternetConnectionProfile();
if (internetConnection != null)
{
    var networkstatus = internetConnection.GetSignalBars();
    Debug.WriteLine("Connection signal strength: " + networkstatus  );
}

this code  get  signal strength only one time that called,

I really want to get signal strength during my app is running real time,

How can I do that? is there any  event trigger for signal changing?

Sincerely,

binhdinh