Help to set up ordering mixed boxes of 12

[Ginger]

Hi, I'm setting up a shop to sell bottles of beers in a box of 12. The minimum order is twelve (a BOX). How do I set up virtuemart so that you can order a box of one style of beer but also if desired a mixed box of beer from a selection of seven - ten different styles of beers. Also the customer can only order boxes of 12, but can order multiple boxes of mixed or same style beers.
Thank you,
Mike