Making an NPC give off a spell aura

[provocating]

When I say "aura" I mean a spell effect, but not actually casting the spell on the player. It does not look as classy when you see the NPC casting the spell. Is there a way of doing this in lua or perl, to have the NPC give off an aura of a spell like levitate when you get in their area?

I know how to do proximity and such, that is easy. I may be over-thinking the problem but let's say you have an invisible man and you want the players to have an effect like levitate when are 250 units from it, normally you would see "so and so cast levitate on Xalmat", I am trying to just get the effect to the player without them seeing the casting.