RM2k3 weapon help

It might be possible... if you have Throwing Knife as an item AND a weapon, and then a common event checking how many you have and taking one away each time a battle skill is used. But I don't know how to do that. BC might, so:

*SUMMONS BLUECUBE*

EDIT: I was thinking of it being used as an item, but in RM2K3 you can't have something as an item that also hurts - unless it is a weapon.