[otrs] How to categorize Tickets - Analyze spent time on categories

Hello List, i would like to "Categorize" my tickets in order to find out how much time we spend on Ticket Categories. E.g. i want to know how much time we spend with Network-Support, Development or Telephone Calls. Is there a way to put Tickets into categories an then analyze how much time we spent on it? (in order to see where the fricking time is going ;) Cheers, Mario