Note that doing this on a webserver is risky, as Excel and Word are not
designed to be called from multiple threads (as a web application will do).
You'll probably run into performance problems as well.
If you're trying to generate these on the fly, you may want to try some
third-party solutions that create Word or Excel format files. If everyone
in your target audience is using Office 2003, you may even try generating
WordML as well.