You could also try using
xinput.
Something like:
$ xinput list
? Virtual core pointer id=2 [master pointer (3)]
? ? Virtual core XTEST pointer id=4 [slave pointer (2)]
? ? Wacom Bamboo 2FG Finger pad id=11 [slave pointer (2)]
? ? Wacom Bamboo 2FG Finger touch id=12 [slave pointer (2)]
$ xinput get-button-map "Wacom Bamboo 2FG Finger pad"
1 2 3 4 5 6 7
$ xinput set-button-map "Wacom Bamboo 2FG Finger pad" 3 2 1 4 5 6 7
