form submission don't have to be handled by email...it's handled by the script that is envoked by the form. The script can then be told to send email...or possibly append to a file. Of course, Excel spreadsheets are binary files (right?) so it'll be a sucker to add on to unless there's some program that does this. Easiest would probably to append to a text tab delimited file, which Excel can import without a hitch.
No clue about front page extensions though, so you're on your own there. I'm thinking perl...