Dumb question: 7 & 9 button mice under Xorg.

[Gain Paolo Mureddu]

    Ok here's the deal... I have a Microsoft Wireless Intellimouse 
Explorer 2.0 mouse. Back in the FC2 days I could use xmodmap to actually 
remap the mouse buttons, as long as they were specified in xorg.conf to 
7 buttons (you know options mousebuttons=7 or something like that, then 
map the z axis to the 6th and 7th button) However I don't seem able to 
do that in Core 3... Why? What's the best way to do this, and where 
would be the best file to place the xmodmap statement?