Cakewalk has released an updated control surface plug-in for the Mackie Control Universal (MCU) control surface. This updated plug-in includes support for the main MCU unit as well as optional XT and C4 units. Thorough document is provided for all units via the online Help

The Mackie Control plug-in can be downloaded from the down load page of the product you own 

SONAR 4 Download page 
SONAR 3 Download page
SONAR 2 Download page