Keyboard Shortcuts for Volume
KeyRemap4MacBook worked with my trackball:

&lt;item&gt;
&lt;name&gt;test&lt;/name&gt;
&lt;identifier&gt;private.test&lt;/identifier&gt;
&lt;autogen&gt;__PointingButtonToKey__ PointingButton::BUTTON4, KeyCode::VK_CONSUMERKEY_VOLUME_UP, ModifierFlag::OPTION_L | ModifierFlag::SHIFT_L&lt;/autogen&gt;
&lt;autogen&gt;__PointingButtonToKey__ PointingButton::BUTTON5, KeyCode::VK_CONSUMERKEY_VOLUME_DOWN, ModifierFlag::OPTION_L | ModifierFlag::SHIFT_L&lt;/autogen&gt;
&lt;/item&gt;


See the source for the key code values and predefined settings.