[CLUE-Tech] starting XF86-4 with diffrent mice?

[Dave Price]

I am running a laptop with XFree86-4.

Sometimes I use the touchpad, and sometimes an external 'wheel mouse'.
I use startx to invoke X, not a GUI login.

I have found that I can get the wheel to work with 'protocol=ImPS2', but
with that protocol, the touchpad is very erratic (i.e. unusable).  

I have been editing /etc/X11/XF86Config-4 to switch protocols, depending
on whether I have a wheel mouse plugged in to the external port.

Is there a correct way to invoke startx and specify the mouse that I intend
to use? (they both show up on /dev/psaux)

aloha,
dave