Fedora Hardware :: Microsoft Keyboard Zoom Function

I have just replaced my ailing Microsoft Natural Elite keyboard which has surprisingly served me well for about 11 years.. I've replaced it with the (wired) Microsoft Natural 4000 which all is working fine on except for the Zoom slider. It'd be handy to be able to map it somehow and so far no luck. There is also the Microsoft 7000 which is a wireless keyboard which appears to have the same slider key. It just creates repeated events when held up or down, nothing really special.

I've tried xbindkeys per some results on google, but it won't map anything >255. I keep reading about "keytouch" but not quite sure how to use it and seems a bit kludgy, but if that's the best solution I can try it again.