You should check out the Excel XML Writer Library and the Excel XML Writer Library Code Generator created by Carlos Aguilar Mares. Carlos downloaded the Office 2003: XML Reference Schemas, ripped the bones of the Excel 2003 XML Reference Schema, and created a C# library that allows you to generate Office 2003 XML Workbooks. If want to see the power of Excel and XML in action, this is a MUST see. This tool is more than fantastic!