[kh99]

I haven't tried it, but I think this will work:

1) In the Usergroup Manager, create 3 new groups "based off of Registered Users", one for each of the forums. You don't need to change any of the permissions.

2) In Usergroups > Forum Permissions, for each forum where you want to control thread creation, click edit next to "Registered Users" and set "Can Post Threads" to No. Also do this for any other usergroups that shoudn't be able to create threads there.

3) Also in Usergroups > Forum Permissions, for each of your 3 forums, click the "Edit" link next to the usergroup you created for that forum, and set "Can Post Threads" to Yes.

4) In Users > Search for Users, find the "thread creating" user for each forum, and add the new usergroup for that forum to the user by clicking the check box in the "Additional Usergroups" section.

The result will be that 3 users will each have 1 secondary usergroup that allows them to create threads in one forum.

There may be a way to do this using access masks so that you wouldn't need the new usergroups, but I'd have to test that to know if it would work.