Permission properties

[Tominator]

Hello,

I'm making a custom permission (you know, for use with CAS) for my
application. I've seen the nice Properties box of FileIO and Security and so
on, my own permission properties show a gray box.
Can I let me input values in a gui too, or do I really need to modify my xml
file, and make a new permission set for every value I want?

I can't look at the xml file of Security for instance, because I don't know
where it is. Searching the internet isn't helping me much either.

Thanks in advance,
Tom