Substituting a mouse button for a mouse wheel?

[walt]

Hi all,

Running xorg-X11-7.2 on gentoo linux.  I have a new Logitec
'Marble Mouse' which has four physical buttons but no wheel.
The two very small buttons are intended to substitute for
the scroll wheel, apparently.

xev tells me that those two small buttons are buttons 8 and 9,
for reasons I don't know.

When I use ZAxisMapping "8 9" then xev senses no events at all
when pressing the buttons, and no scrolling takes place.

But, when I do xmodmap -e "pointer = 1 2 3 6 7 8 9 4 5" and
then use ZAxisMapping "4 5" the scrolling works.

Only one problem left:  each button click generates one event,
and so I need to click the button multiple times to get any
scrolling done.  Is there a way to make a sustained button
click generate multiple events, the way a keypress does?

Thanks!