map / detect axis3 as digital key

[Soundix]

hi-

I've this problem, can't map axis3 (it's the right analog stick left/right movement - a dualshock1 with raphnet usb converter) to a game key

in the joystick configuration this axis work fine if I set for looking/turning etc..
i've tried to edit the config file, writing axis3 but as expected it won't do the trick
example:
axis3plus=invprev
axis3minus=invnext

is there some workaround ? maybe with aliases or something ?
thanks !