How to create a small list of custom rules, but for only certain forums?

[CBrown]

Basically what it says in the title. We have rules, and I see the CYB - Advanced Rules, but that's not exactly what I want.

I'd like a small set of text for forums where people can buy/sell stuff, so rule there don't really mean much elsewhere.

But how do I go putting some "set text" before someone creates a thread in 3 different forums, but not the rest of the site?

Is that possible?

I'm searching the mods, but don't see anything jumping out at me. I would think a template mod might work, but just don't know how to go about it.