public static void Hide(Form frm)
 {
     if (frm.InvokeRequired)
     {
         FormCloseCallback d = new FormCloseCallback(Hide);
         frm.Invoke(d, new object[] { frm });
     }
     else
     {
         frm.Close();
     }
 }
 private static void FormClose()
 {
     if (rtmbform.InvokeRequired)
     {
         FormCloseCallback fccb = new FormCloseCallback(FormClose);
         rtmbform.Invoke(fccb);
     }
     else
     {
         rtmbform.Close( );
     }
 }