Hi Keith, never did something like that, my Omnibook has just two buttons, but I think I can give you some pointers, since we don't have many topics about this issue in the forum.
First you have to find out how the buttons are recognized by the system. Open a terminal and run the xev command. It will draw a white window, focus on it and press the buttons. You will get in the terminal something like this, between many other things, just find the line with "button". It will look like this:
ButtonPress event, serial 26, synthetic NO, window 0x1800001,
root 0x1a6, subw 0x1800002, time 11045186, (42,41), root:(43,58),
state 0x10, button 1, same_screen YES
Here I pressed the button 1

. Do the same with the other button and write down both numbers.
Then as root, open your /etc/X11/xorg.conf file with your favorite text editor, and find the line which says:
Option "ZAxisMapping" "4 5"
Replace "4 5" with the numbers you got from the xev output.
If there is no such line, you write it on the InputDevice section for your mouse, it looks like this:
Section "InputDevice"
Identifier "Mouse1"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/mouse"
Option "ZAxisMapping" "4 5"
EndSection
After this you have to restart the X server, close all your apps and press CTRL+ALT+BACKSPACE. Login again, test the thing, and hopefully... enjoy.