Magento installation (ver. 1.4.0.1) that need customization so that a a minimum quantity of a category of items is added to cart before checkout is possible. This quantity can be any number of different items in a single category of products. Other category of products are not affected by this minimum quantity requirement.
This Magento installation already uses this module:
http://www.magentocommerce.com/magento-connect/webshopapps/extension/1893/webshopapps-cross-product-price-tiers
for tiers pricing applied to the same category of products where the minimum quantity is required.
