Autocopy backup of NEW files in a directory

Win2K3 SP1 or WinXP Pro SP2
How can I automate a copy for a file that an application writes to a
directory and copy this source file from the source directory to a backup
directory AND rename that copied file?

For example, the application writes a file into D:\ApplData\Invoice.csv and
I want to copy this Invoice.csv file to
D:\ApplData\Backup\Invoice2006-10-25-09151000.csv (where there's a date and
time stamp to maintain uniqueness). I'm not requiring the date/time stamping
but the backup file needs to be unique as the Invoice.csv file is the
standard name for the original file name. Invoice.csv is written out several
times a day and throughout the week/month etc.

Is there a utility or way to do this once the Invoice.csv file is written
out? I'd like to do the backup/copy for other files in the same directory.
Not all source files are created at the same time.
TIA,
Tom