[CentOS] Logitech Marble Mouse on CentOS 4

Hello there!

I just bought this trackball and connected it to a CentOS 4 box. I  
googled on how to edit xorg.conf for the 2 scrollbuttons, and they  
work while using this section:

Section "InputDevice"
         Identifier  "Mouse0"
         Driver      "mouse"
         Option      "Protocol" "ExplorerPS/2"
         Option      "Device" "/dev/input/mice"
         Option      "Emulate3Timeout" "50"
         Option      "Buttons" "7"
         Option      "ZAxisMapping" "6 7"
         Option      "Emulate3Buttons" "on"
EndSection

But then the left button is for scrolling up, and the right for  
scrolling down. How can I reverse this?? I have tried several  
sections from the internet, but most have the same result or don't  
work at all.

Thanks in advance for any help and/or tips.

Angelo