OSTicket does not inherently have built in support for what it sounds to me like you are asking. However there are a number of Mods in the Mods forum that may assist you in achieving this goal. Installing mods does mean that you should probably have some basic PHP coding skill so you understand what your doing.
You should probably look at:
http://www.tmib.net/content/osticket-16-how-add-db-populated-drop-down-and-admin-interface-version-10(http://www.tmib.net/content/osticket-16-how-add-db-populated-drop-down-and-admin-interface-version-10)
http://sudobash.net/osticket-auto-assignment-rules(http://sudobash.net/osticket-auto-assignment-rules)
You can find these two and more in: http://osticket.com/forums/forumdisplay.php?f=9(http://osticket.com/forums/forumdisplay.php?f=9)