This is a fine section to post in.
There are some menu mods out there, one may do what you want:
Phil has a bunch:
http://www.xcartmods.co.uk/x-cart-mods/
Here is one that some swear by:
http://www.thexcartstore.com/xmenus-menu-manager-xcart.html
However to do this exactly the way you want, you probably need someone to custom code it. I'd be interested if you need help in this arena.
Hope that helps.