It should work. On a laptop, there are two mice. The regular mouse and the touch pad.
You need separate "InputDevice" sections for each mouse -- with unique idenifiers. The "Screen" section will need to refer to both identifiers.
Here is the "Screen" section from my laptop's xorg.conf file:
Code:
Section "ServerLayout"
Identifier "Layout[all]"
InputDevice "Keyboard[0]" "CoreKeyboard"
InputDevice "Mouse[1]" "CorePointer"
InputDevice "Mouse[3]" "SendCoreEvents"
Screen "Screen[0]"
EndSection
I don't know however if the "Mouse[3]" entry says "SendCoreEvents" because it is the second mouse, or if it is because it is a touchpad.