make new users present themselves

[ciocsy]

i want to make my new users to post in a thread called "about us"
something like a presentation about themselves. is there any way i can make them to do that?

my idea was something like this: showing a text under the navbar, that tells them to go the thread and write about them.

how can i do that? and how can i make the text show up only for the users that didn't write into the thread.

is it possible?
any other ideas?
thanks!