[Plugin: WP-prettyPhoto] menu question. how to launch external link in pretty photo?

Trying to get an external link on my menu to open in a prettyphoto box. let’s say the external link is http://www.google.com . I want to click on the menu item – call it Search, and I want the google window to open in a prettyPhoto modal window. I have added wp-prettyPhoto to the class box in the menu item, and it still doesnt work. I have tried to use this url: http://www.google.com?iframe=true&width=100%&height=100%. also doesnt work.
Ideas please?

http://wordpress.org/extend/plugins/wp-prettyphoto/