Excel (2010) has functionality to create pivot tables from an external data source like from Access, From Web and other data sources like SQL server and ODBC. Suppose I have created a new database system called X and I want to create the functionality that Excel can connect to this X using a data provider (not an Excel Add-in). What do I develop and where do I start?
Excel can use any ADO.NET driver If I'm not mistaken. So all you need to do is to follow the following guide. Here is a more detailed description from MSDN Magazine.
You'll need to create an OleDb driver if Excel doesn't support ADO.NET drivers.