2 column drop menu

Hi all

I'm currently creating a new website for the school that I teach at using montezuma. So far I'm managing to customise most aspects as I want but I'm struggling with the drop menu or level 2 items. I have one menu with a large number of items which when viewed on a notebook spreads off the bottom of the screen making the menu items inaccessible. What I want is to split a drop menu with over 10 items for example into 2 columns so that they are all visible on screen. Any ideas?

Thanks