Detecting a Buff

Is there any way to detect a specific buff on a unit? The only functions I could find just checked what kinds of buffs etc the unit had. =/ Anyone know..? I need to stop people from casting the same spell on the same person over and over because it is a trigger-made spell that stacks.

Thanks

Boolean comparison - unit - unit has specific buff. I believe this is what you are looking for.

Ahh stupid me didnt look in the boolean section LOL. Thanks a bunch!