public void RunPopUp(NSEvent theEvent)
        {
            // create the menu the popup will use
            NSMenu popUpMenu = this.Menu;

            if (popUpCell.Count > 0)
            {
                NSMenuItem item = popUpCell [0];

                if (item.Title != "")
                {
                    popUpMenu.InsertItem("", null, "", 0);
                }
            }

            popUpCell.Menu = popUpMenu;

            // and show it
            popUpCell.PerformClick(Bounds, this);

            NeedsDisplay = true;
        }