As in scrolling up and down at the same time for HS.

You don't scroll up and down at the same time. You can bind fire to both scroll up and scroll down, and then you can scroll up, scroll down, scroll up, scroll down, etc. It's just so you don't have to take your finger off the scroll wheel to start another scroll.

http://www.speedrun.com/Antichamber/guide/erlq5#ch3Bind_Fire_to_ScrollWheel

Thanks, that's what I meant I just couldn't quite say it correctly at the time.