I need to have more control over custom profile fields

[Justice]

I'd like to be able to make a custom profile field a drop down menu or button select instead of just a text input. There are certain fields that I need to restrict my users to only a select few choices. In UBB, every extra field was manually added through hacks, but vB creates them automatically. While this saves a lot of time, it also leaves me with less control.

An example of this would be using "Gender" as a custom field, and only having 'male' or 'female' as selectable choices, so they couldn't type in "transsexual" or something.

I have a few fields that I'd need a pull down menu for. How would I set that up?

(It seems like every time I post a "How Do I" question, I get the feeling it belongs in the hack request forum, but I'm not really sure)