eq on just a small section of a track

I'm trying to learn a new thing. Theres a keyboard track and my friend wants the treble pulled down on just certain parts of the track.
 
So I created a new bus and put a treble killing EQ on the bus, and the output of the bus, to the master bus. Then I created a SEND from the keyboard track, to the bus.Turned on the level and post buttons on the SEND.
 
When I raise and lower the slider on the bus, I would expect the EQ to take effect. But it doesnt,... the only thing that happens is the volume of the track gets louder.
 
Is there a tutorial or something or a video or anything, that will fully explain this technique? I cant figure out why it doesnt work.

OK, I dont know how to do that. I right clicked the track, add envelope, but EQ was not one of the options.
 
Can you please explain how I could do that?

The best way is to route the synth to a bus. Set the high shelf of your eq where you want it, the activate the "write" button. Press play and cut the level on the the high shelf like you want it while the track is playing. Then when you're done turn the write button off, and make sure the "read" button is on. Now when you play it back the eq should move exactly how you did while you were writing the automation. If you need to, edit it by clicking on the clip automation in the track view. Hope that helps. Let me know if you need any more help.

Glad to help!