I am using Xorg7.3, and I have a Saitek gaming mouse, with 5 buttons detected, but the two last buttons are detected as button 8 and 9 by xev.

My mouse is configured like that :

Option "buttons" "7"
Option "ZAxisMapping" "4 5"

Wheel works fine.
I can use buttons 8 and 9 in a game like quake4 ( detection is ok ), but in an app like firefox, they are used exactly like button 1, they just do clicking, so I cannot use them to make previous et forward as example.

I tried to reconfigure the mapping with xmodmap, but it gives me an error when a want to mention ids 8 ans 9 in the pointer string.

What can I do to change theses buttons IDs ?