Additional Terms & Conditions for certain categories

I'm new here, so apologies in advance if I'm asking about something that already exists but I can't find it or if I have posted in the wrong place.

We have 3 categories in our forum and will soon be adding a fourth. We want any users who access the new category to confirm that they are over a certain age to access this part of the forum. The plugin can be such that it asks this question either every visit or just once.

Do any of you knw if this exists or does anyone fancy developing it?

Thanks :-)
Paul