How to get focus on toolstripDropDownButton.

I have toolStrip Control, and it has few items like toolstripButton, ToolStripDropDown button.
For ToolStripDropDownButton i am not creating any dropDown list, instead i am using contextmenu with few items.
Whenever mouseHover to this toolstripdropdownbutton i show this contextmenu.
here is sample code

private void toolStripDropDownButtonOpen_MouseHover(object sender, EventArgs e)
{
    ToolStripDropDownButton btnSender = (ToolStripDropDownButton)sender;
        Point ptLowerRight = new Point(btnSender.Bounds.Right - 95, btnSender.Bounds.Bottom + 16);
        ptLowerRight = PointToScreen(ptLowerRight);
        contextMenuStrip.Show(ptLowerRight);           
        
}

I want whenever i loose focus on toolStripButtonDropDown that time this contextMenu should be closed. I have used mouseleave event for this but its not working properly.
Any help will be appreciated.
Thanks in advanced

Tags: C# 3.5, ToolStrip, DropDownList