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?

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To make an answer from the OP's comment.

The installation procedure can be found here.