check case of filename when adding

Hi,
We have a CVS server running on Linux but the clients are running on
windows. We seem to experience problems with the casing of the filenames
(two files got added with identical filenames but a different case).
I was wondering if there is a possibility to prevent this from adding.
I know I can write a pre-commit check script that solves this, however, I
would like to do it when the file is added (commit-time is somewhat late in
the process).

Can anyone point me to a solution ?

thanks,

Piet V.