The Mackie Control Universal uses MIDI to control Adobe Audition, so you need MIDI ports on your computer, and a pair of MIDI cables. Edirol makes several MIDI/USB devices that you can plug into a USB port on the computer. Many sound cards and interfaces include MIDI ports, so that should not be a problem.
The Mackie has to be version 2.1.2 to work with Audition. Mackie has a download for it at their website, with a Readme file that tells you how to configure the Control for upgrading. Basically, you play a MIDI file into the Control to upgrade the firmware, and this is a problem because Audition won't play the MIDI file! So you use Windows Media Player instead, which works fine, as long as you have selected the correct ports for it in Start/Control Panel/Sounds and.../Audio (MIDI out).
Once the firmware is the right version, go to Audition/Options/Device Settings and select the Mackie in the "External Controllers" tab. Click on "Configure" and then "OK." Then go back into Options/Device Settings/MIDI and select the MIDI ports you have on your computer as the I/O (you need both, since the Mackie and the software talk to each other).
When you get ready to record, turn on the Mackie before you start up Audition, so that Audition will recognize that it's there.
I've been using the Mackie and it's great. Very well made, good looking (for what that's worth) and intuitively laid out, with the help of the Lexan overlay (which is still labeled "Syntrillium Cool Edit Pro"). I went from a Syntrillium Red Rover to Tascam US428 to Mackie, and it was a big step up each time.
Now if only Adobe would allow you write volume/pan envelopes from the Mackie....
"Digo: 'paciencia, y barajar.'" -- Don Quijote de la Mancha, Part II, Chapter 23