Thumb-down dragging in Ubuntu Maverick on newer Macbook( Pro)s is currently supported only by the new, currently non-configurable, but quite functional independently written "multitouch" X input driver from the mactel PPA. (Canonical hasn't written utouch support for MB(P)s yet.)
From one of the official Macbook or MacBook Pro Maverick hardware support pages--
To enable the multitouch drivers, add the mactel ppa:
sudo add-apt-repository ppa:mactel-support && sudo apt-get update
Then run this in a console:
sudo apt-get install xf86-input-multitouch bcm5974-dkms
Then add this to the new file /usr/share/X11/xorg.conf.d/99-multitouch.conf (on Maverick and later) with the same permissions as the other files in the directory:
Section "InputClass"
MatchIsTouchpad "true"
Identifier "Multitouch Touchpad"
Driver "multitouch"
EndSection
You can then get three-finger gestures working using mouse "buttons" 8, 9, 10, and 11 (use xev to view them) via imwheel (Ubuntu universe). I'm going to finish that part another day, though xev is clearly showing the "press" of the "buttons" to indicate it's ready to be hooked up.
To see if this applies to your model, you should go to Ubuntu.com Help Community MacBook or MacBookPro page and find your system, or something close to it, for the Ubuntu version you are using (stick to the correct version!) in the grey box on the right at the top. Currently, many of the systems have out-of-date or incomplete information. However, Apple changes little between versions, so you'll be able to use information from almost any machine's page (read them all!). The MacBook Pro 7,1 Maverick page has the most complete information for Maverick as far as I've seen, though the Maverick MBP 5,5, 5,3, and 6,2 pages also have info not found elsewhere that I needed. That's where this information came from.
More info on PPAs:
Best Answer
Isn't this doing what you want?
This is in System / Preferences / Mouse.