How do I create an Excel add-in that reads custom data?

Programmer Question

I have been tasked with creating an addin for Excel 2007 that reads data from a custom data source. I already have the code that reads the data. It's written in C# and returns objects. This is for a banking system and I cannot give direct access to the data. A userID, password and hardware generated key must be provided to the C# DLL to get up to date data.

My boss wants the data to be updated automatically once per minute or manually using the Refresh function provided by Excel. So I need to make the data appear in Excel as if it were from a standard database connection.

I've looked around for a starting point but I am struggling to find some information that will help with this very specific requirement. Can anyone help?

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