Excel Workbooks/Spreadsheets in MOSS

Question

Hi,
 
   I don't know whether my problem fits in Excel Services or not. My problem is not just to open Workbook/Spreadsheets in Sharepoint but I have to bring whole current account application which is based on several Excel workbooks/Spreadsheets working on macros. These spreadsheets are heavily equipped with macros having complex formulas/logics.  I know how to import excel sheet into sharepoint as a custom list but what to do about the macros and functionalities to carry on.  Do I need to import excel spreadsheets as a custom lists into sharepoint and then have to re-write macro functionalities as custom rules and workflows attached to these lists?  I want to know what are various ways to accomplish this task and their advantages and disadvantages. Also, What would you recommend is the best approach to do this.

I would be very grateful, if you can forward me any resource that can help me to dig out more about this topic to explore. 
 
Thanks & Regards,
Khushi

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KhushiSShaikh