You could trigger it. When user uses an item with dummy ability, you could add auto-cast faerie fire or something in disabled spellbook. When faerie fire is cast, simply make dummy cast chain lightning. When you use an item again or looses it, simply remove spellbook from your unit.
I am not 100% sure that this works, but it most likely does so. If you want, I could make you JASS or GUI trigger (prefer JASS) for it.