Assigning extra mouse buttons (eg. MX Ergo trackball)

[jonetsu]

Hello,

Got a 'new' Logitech MX Ergo trackball ... Is there a way to assign the
two extra buttons within emacs ?  When pressed emacs shows 'mouse-8' and
'mouse-9'.  Nothing much so far but I'd like to assign them to page up
and page down.

Another feature that could be useful is that the scroll wheel can also
be clicked sideways, one click when titled left, one click when tilted
right.  In this case however emacs does not show anything at all in its
status bar.

xev will show these as buttons 6 and 7:

ButtonPress event, serial 37, synthetic NO, window 0x5000001,
    root 0x115, subw 0x0, time 7662467, (89,97), root:(800,619),
    state 0x0, button 6, same_screen YES

ButtonRelease event, serial 37, synthetic NO, window 0x5000001,
    root 0x115, subw 0x0, time 7662467, (89,97), root:(800,619),
    state 0x0, button 6, same_screen YES

ButtonPress event, serial 37, synthetic NO, window 0x5000001,
    root 0x115, subw 0x0, time 7663797, (89,97), root:(800,619),
    state 0x0, button 7, same_screen YES

ButtonRelease event, serial 37, synthetic NO, window 0x5000001,
    root 0x115, subw 0x0, time 7663797, (89,97), root:(800,619),
    state 0x0, button 7, same_screen YES

Is it possible to bring buttons 6 and 7 to emacs ?