Adjust sensitivity of trackball in Linux Mint 13

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http://unix.stackexchange.com – I am using Logitech Trackball Marble and I have difficulty adjusting the sensitivity of it in Linux Mint 13. Apparently the sensitivity and acceleration setting in Linux Mint only work for the mouse. ( I have both mouse and trackball plugged) How can I adjust it? I searched about it in google but find no useful result. I've seen people digging in something called xorf.conf but I have no idea what it is. I check my /etc/X11 directory and found no xorf.conf but only some file looks like xorf.conf.fail (HowTos)