Weapon hit spell ???

I've tried to use the ingame tools to allow a character to use a weapon that occasionally would cast a spell on the foe after a successful hit. Ex. using an ice sword gives the player a 25% to have an additional ice spell damage effect immediately after the hit. If anyone has figured out how to do this with the stock tools, I'd love to see it. Otherwise, I'm sure it can be done with a plug-in.

My original method: Had the ice sword place an invisible state on the foe and had the battle event looking for it. If it was found it would call in an animation, damage the foe (which didnt seem to be visible) and then remove the unseen state. Unfortinately this didn't work...