Excel 2007 has a server feature (Excel Services).
It's not quite straightforward, but it's there and was developed just to do what you require.
There are several blogs where you can find more information, here's one:

http://blogs.msdn.com/excel/archive/category/11361.aspx

--
Kind regards,

Niek Otten
Microsoft MVP - Excel



wrote in message ...
|I am looking for a server based spreadsheet. I'm not talking about an
| online spreadsheet like google.docs but a software I can install on my
| own server. The only package of that kind I found so far
| http://www.simple-groupware.de/cms/Spreadsheet/Home lacks some key
| features I need.