[SONAR X3] Using a gate to enable EQ?

I recorded a vocal concert in a church. Sounds great, but nobody could find the caretaker beforehand to get the air conditioning shut off. The hum is fairly well masked when people are singing, but as soon as they stop singing, the hum becomes pretty apparent.
 
I can reduce the hum with an equalizer, but it's around 120Hz, so even with the band Q set up as high as it'll go, it erases the basses whenever they're singing a B at 123Hz.

Is there any way to automate the equalizer so that it enables whenever the volume drops below a certain level, and shuts off when the volume exceeds that level? I thought maybe there would be a way to do that via side chaining, but it looks like only gates and compressors support that.

tlw
The Sonitus gate can be side-chained, and in a frequency-dependent way.

 
Right, but I don't actually want to gate the sound (because that kills the echoes); I was hoping I could use a gate to control an EQ effect's enable parameter rather than actually altering the sound itself.

 

1st, the person offering to run it through RX- take the up on it.
2nd, using an expander/gate on a certain frequency range is an interesting idea.  let us know how it goes if you figure it out!

I'm not a hundred percent sure and I don't have hours to spend on it but it's pretty good and I'd gladly give it a go if you don't mind going through the trouble of sending me the file. Maybe PM me to exchange email addresses if you feel like it?