MIDI knobs and sliders with Garageband?

I have two MIDI devices connected to my computer. One is a standard 88-key piano keyboard. The other is a device called the EasyControl.9, which provides an array of knobs, sliders and buttons.

The keyboard certainly works fine in Garageband but I can't get any of the controls on the EasyControl to do anything. I expected that at least some of them would have the effect of changing some of the controls on various software instruments, in particular the synthesizers. But nothing happens.

EasyControl comes with an application that allows me to remap the controls to different MIDI numbers, but I don't know which numbers to use or which ones Garageband will react to.

Thanks,

Frank