Final Fantasy Hacktics

Does anybody know of a way to make the Cannoneer's Potion Shell consume a Potion from the the player's items, and Ether Shell consume an Ether from the player's items? I'd assume I'd have to use hex editing, but I don't have the proper addresses to start with, nor do I know the data values to mess with if I did. Has anybody ever tried to make an ability consume an item before? Or perhaps have an ability access the items menu? If so, perhaps they could help. Any help or guidance that anyone could offer would be appreciated. Thank you.