detect scroll lock key status change?

[Zhang Weiwu]

It would be wonderful if in my web application, a user can simply press
scroll lock to get a clean view, e.g. without navigation bar, menu bar
and extra buttons, so the user can concentrate on the content. After
he/she press scroll lock again the page goes back as it was.

This web app is only used in our company where everybody use firefox
(because it's designed that way), so a firefox-only-solution is acceptable.

Any good idea? Scroll Lock are two frequently used words, no wonder why
I failed to STFW any useful information.