In your sample you also have to deal with whether you are doing the function registration yourself (with code in AutoOpen() as you have it now) or let Excel-DNA do the default registration.
Currently you have both, leading to warning messages popping up.
To disable the default registration, you would set this property:
<ExcelAddInExplicitRegistration>true</ExcelAddInExplicitRegistration>The supported project properties are listed here:
-Govert