I've created an excel Automation Add-in that exposes some functions in an
Excel spreadsheet. I have a setup project for this, but it does not seem to
register the classes correctly.

How do I create a setup project to install an Excel Addin?

My project is in C#,

namespace Myplugin
{
[ClassInterface(ClassInterfaceType.AutoDual), ComVisible(true)]
public class MyClass
{
// members


// exposed function
public decimal last(string symbol, string region)
{
}

[ComRegisterFunctionAttribute]
public static void RegisterFunction(Type type)
{
Registry.ClassesRoot.CreateSubKey(GetSubKeyName(ty pe));
}

[ComUnregisterFunctionAttribute]
public static void UnregisterFunction(Type type)
{
Registry.ClassesRoot.DeleteSubKey(GetSubKeyName(ty pe), false);
}

private static string GetSubKeyName(Type type)
{
string s = @"CLSID\{" + type.GUID.ToString().ToUpper() +
@"}\Programmable";
return s;
}