CSV, Milliseconds default formatting of mm:ss.0

When I generate some CSV files I need to include milliseconds. When anyone
opens the file in Excel (in my case part of Office 2003, SP2) the datetimes
appear with a default formatting of mm:ss.0. This is frustrating and appears
unprofessional on my part when clients open the file. They assume I have
made some sort of mistake.

I have already thought of generating using
=DATE(blah)+TIME(blah)+millis/(24*60*60*1000) but I don't like the idea.

How can I change the default format so that it would be something more
sensible and my clients and I could avoid the drudgery of clicking on the
column header(s) and manually formatting?

I have googled, I have searched my registry and regional settings. Nothing
that I could find helped at all.

Please see the attachment for a demonstration.

Thanks,
Chris Pankhurst