Excel on a web server
 

Our project has a need to drop an Excel workbook in an IIS server; this
workbook has many calculations, macros and formulae. We would like to open
this Excel workbook when a specific web page is requested - user would have
provided data in the web page that is the input to the Excel workbook. The
Excel workbook would be opened for calculation, after the calculation the
data will be passed out as a Response and the workbook closed.

This needs to be done for multiple users. Here are some questions:
1. Had anybody done this before?
2. If so, what are some consequences of doing this?
3. Is there a different way of doing this? We are aware of Excel Web
Services (part of SharePoint); we are not considering this solution for
reasons that are not relevant to the current question.

I would love to hear how you did this and what kind of performance issues
you have seen.