Bukkit

Minor issue: Is there a way for the shop owner to set the amount of a particular item he is willing to buy? I know that you can simply put in only the amount of currency you want to spend in the shop's inventory, but that solution assumes that only one item is being bought by the shop for each currency. For example, say I own a shop that buys diamond hoes and porkchops, and both deals trade in gold nuggets. I probably won't need a lot of diamond hoes, but I might want to amass a large supply of porkchops. How can I make it so that the store only buys a set amount of hoes so that it has money left over to buy porkchops?