Need to determine if a user is viewing a particular forum
 

I've recently added an extra forum category for Traders information on my site and i want to display a message to just registered users when they are viewing that forum, maybe just a small table above the forum.

Reason behind this is i have set up a usergroup for Suppliers that gives them permission to use that forum as normal with the option of deleting own posts but registered users cannot post new threads in there so they can only reply to existing threads to save on the area getting cluttered.

How can i determine a) if the user is a registered user? (i only want registered users to see this) and b) whether they belong to the Suppliers usergroup? as i dont think they will want to see it either :)

Thanks