What functions file is associated with postbit?

[binjured]

Hey all. I need to know which functions file is associated with the postbit / postbit_legacy template. I'm modding my postbit_legacy (specifically the username menu dropdown) but it's going to require a variable or two in addition to simple html changes. If there is no functions file associated with the template, is there a way to make one that is? Also, do I need to specially define my variables to make them work in the template, like do they need to defined as "global" or anything?

Thanks.