Microsoft Office 2010 Excel Add-In (or UDF)

I have created an automation add-in with a UDF that converts a given number into a string (ex. 100 = one hundred); like a cl开发者_Go百科ass library in Visual Studio 2010 in C#, and it works with MS Excel 2007(x86). I am having a problem when I install it on MS Excel x64. I have created the add in using this blog post.

Where and what should be changed to make this thing to work?

To make an answer from the OP's comment.

The installation procedure can be found here.