Charm spell cast on a charmed NPC

[AxeMental]

If an NPC has been charmed by a monster (or a charm effect such as that of a harpy, or other monsters that have a similar "control" effect), could an MU then cast charm person on that same NPC to attempt to nulify the monsters charm (in effect charm the NPC away from the monster). IYO is this a valid way to negate the effect of a harpy for instance (assuming there was an MU around to cast the spell)? I would tend to think definitely if its an enemy MU, if its a monster casting charm person I think it would probably work as well. But I'm not so sure about charm effects. As DM I could go either way in this.

[TRP]

The character is then under the effect of two spells, and he will view both casters as very friendly. Nothing is negated.

[vikingv]

I concur. Of course, in this situation, orders to combat another 'friend' will cause new saving throws.

[Matthew]

This feels like a familiar topic, did we not have this same discussion recently? For what it is worth, I agree with The Red Priest.

Ah, here we go Dueling Charm Person Spells

[T. Foster]

Since Matthew helpfully found the previous thread on the same topic, I don't have to bother to re-type my opinion from there (which I still hold)