Spell mod that spreads like wildfire

[captianoreohead]

I've just started working on my first mod as a request from a friend, it's supposed to be a spell that you cast on an NPC then they are forced to use the same spell on anyone they see and then after a few minutes they just die.

The only problem i'm having is I don't know how to force the character that gets hit by the spell to be forced to use that spell, but not any other spells or weapons.

Any help would be appriciated.