[CentOS] Enhancing the mouse support

I've been looking around for info on how to enhance the mouse support in a newly installed CentOS5 system and all I've managed so far is to get more confused.

It seems that the "evdev" driver is a necessary tool but to compile that requires an xorg SDK which I can't even find. I've probably used up more than my fair share of Google searches for the weekend on this one, thought I'd ask and see if (hopefully) I'm missing something truly obvious and simple.

The end result I'm looking for is to be able to map the extra buttons on my trackball to whatever event I'd like it to do. So for instance there's an extra button next to my left mouse button that I'd like to map to a double click event.