My current computer is on its last legs. I'm getting a new computer shortly and was planning on setting up a dual Win2K/Linux boot eventually, but that may be a while.
Here's the reference I mentioned above:
L. Stein & D. MacEachern, "Writing Apache Modules with Perl and C", O'Reilly, 1999, ISBN 1-56592-567-X, Chapter 6 (Authentication and Authorization).
Apache modules can be written in either Perl or C. I think Perl is preferable, unless you need it to be really efficient, which probably isn't the case here.
You might also check apache.org. Maybe something like this already exists.