Using FrontPage on a secure directory

Front Page 2000/Windows 2000/IIS5.

I have site which has a secure directory. In other words, all the site
http://www.mysite.com is accessible by anyone, *except* the directory
and subdirectories http://www.mysite.com/secure. All this is working
fine.

Users in "securegroup" are the only ones given permission to the
relevant directories.

However, the users in "securegroup" should be the only ones able to
update the relevant directories *and no other directories* using
FrontPage.

After trying many *many* options, I can allow the "securegroup" to
update all directories using FrontPage, or none. I can't find a way to
configure it so that they can **only** update the relevant
directories!

Is there a way to do what I want? It used to work in NT4!

Cheers,

Cliff