By default, a magic skill gives you the choice to target a monster. And a simple way to make a multi-hit spell would be is to either make it a random hit field damage or keep attacking a single monster until it is destroyed. But what I have yet to discover a way of accomplishing would be a spell that allows you to target a monster, and then use variables (or something) to make a spell hit said monster more than once without having to re-cast the spell. Does anyone know how something like this can be done? Also, this is being worked on in Rm2k3.
Doing that would probably take a lot of common/battle eventing. I don't think you can make a spell hit more than once off the given system, I do know, however that it is possible (There's a youtube video, I'll post it when I can find it).
Nevermind, it turns out simply setting a combo to a battle command does exactly what I was looking for.