A couple of notes, first of all this is no a
great way to do security. Far from it actually.
Its trivial to change your User-Agent in most
browsers. So this really only works if people
play nice. There are a number of ways to do 
most things, this just happens to be another.
Here is an example:

<VirtualHost *>
    ServerAdmin root@localhost
    ErrorLog logs/dummy-host.example.com-error_log
    CustomLog logs/dummy-host.example.com-access_log common
    AuthUserAgentDeny *Mozilla*
<Location /test>
	AuthUserAgentAllow *Mozilla*
</location>
</VirtualHost>


Its pretty trivial, I hope it works for you.
	-Brian Aker  (brian@tangent.org)
	Seattle, Washington.