How to duck a single audio channel?

The documentation and videos I watched showed how to duck volume of one channel in relation to another, but I'd like to duck just one audio channel if it gets too loud. I have multiple SFX that play through one channel with PlayOneShot, and some can be much louder than others. So I'd like to duck that channel's sound to the level of the quietest SFX clip. How do I do that?