How do I make the ASP.Net menu control selection clear after opening a new page?

Question

I dynamically add menu items in my page_load method.

Menu1.Items.Add(new MenuItem("CNN", "CNN", string.Empty, "http://www.cnn.com", "News"));  

When I click on a menu item that goes to an external page and switch back to my page, the menu item remains highlighted. How do I open a new page and clear the selection?

-- Edit --
For now, we're pointing to an internal page with an IFrame. I'd like to leave this question open in case someone finds a better solution.