[otrs] Stats

Hello all: I'm the same guy who asked about HTML mails :) Now I've another question. I need to create more stats than OTRS have, and in the manual I couldn´t found anything about it. Where are stats, how can I add another Stat?. I supose That I may change at least one table and touch some code, but I can´t found where. Can anyone help me?. Thanks Alvaro.