Add user defined function to Visual Studio Excel Add-in

Question

In visual studio I have an Excel 2010 Add-in project. How can I have that project create the following module:

Answer 1

If what you really want to do is to write .NET UDFs, or a combined .NET application level command and UDF addin then using VSTO is not currently a good solution:
I would recommend using either Addin Express (costs) or Excel DNA (free).
Both of these allow you to create both .NET XLL UDF addins and Automation UDF addins (XLL UDF addins offer significant performance advantages but with slightly more restricted access to the Excel object model)