[otrs] add my own drop down to a ticket

Hi guys, Can I add my own drop down to a ticket so I can select the category when creating a ticket and get a categozied result when generating a report? I know I can use service ->SLA to add a tree which I can select from. However, I want more than one categorization. For example, I want a ticket to select "Windows->logon->cannot logon" as "service" and "SLA". Meanwhile, I also want an agent to be able to select some other informaiton that I am interested like a drop down called "frequency" where I can select something like "only once", "occationally" or "can be reproduced". I may want to add a third dropdown to select something else... Is there anyway to do this? Thank you for any help you may provide. Sincerely, Andrew