//WINDOW MESSAGE HANDLER
 protected override void WndProc(ref Message m)
 {
     base.WndProc(ref m);        // call default p
     if (m.Msg == (int)ApplicationInstanceChecker.MSG_ID_SEND_MESSAGE)
     {
         ApplicationInstanceChecker.ShowWindow(Handle, 1);
         ApplicationInstanceChecker.SetForegroundWindow(Handle);
     }
 }