uh you can buy or build
if you want to build, you can use clientside Office Web Components.
does it NEED to be web-based?
i personally prefer real excel automation against real XLS files that end users can save wherever they like.
my team develops webbased reports using OWC. it is a great way to go. it might frutstrate you. it might take you a year.
but at the end of that year, you will have some very powerful flexible reports.
these are the best MD ActiveX controls anywhere.
if you buy, you are on your own, and be prepared to spend big $$.
Access 2002 ADP Rocks my World
Long live SQL Server and 64bit Windows!!!