We'll need to install xbindtools and xev prior to configuring our mouse buttons:
sudo apt-get install xev xbindtoolsFirst, find out what button number you are trying to set using 'xev'
This can be run from the command line simply by typing 'xev' - the tool will popup in a separate window. Mouse over this window in order to test the keys and watch the command line output to find the button number.
Then write a config file to handle the key you want to change. For example, on my Performance MX, I wanted to set the "zoom" button to "back":
cat << EOF >> ~/.xbindkeysrc
"xdotool key Alt_L+Left"
m:0x0 + b:13
EOFNext, reload xbindkeys in order to activate your changes:
xbindkeys -pIf you have a wireless mouse you can run this configuration elsewhere with the following file:
#!/bin/bash
sudo apt-get install xbindkeys
cat << EOF >> ~/.xbindkeysrc
"xdotool key Alt_L+Left"
m:0x0 + b:13
EOF
xbindkeys -pMuch of this was cribbed from the following answer on AskUbuntu: http://askubuntu.com/a/101126