Using an enum typecoverter in an Excel PIA DLL

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I would like to use a TypeCoverter to regionalise output for enums in an
assembly that is a PIA loaded into Excel.

I can run this and it works on an assembly in a test project I created with
an explicitly referenceed assembly, however when running a project that has
been built as an Excel PIA. If I try:
<System.Compone ntModel.TypeCon verter(GetType( ResourceEnumCon verter))_
public enum MyEnum
ItemA
ItemB
end enum

and in code
myE = MyEnum.ItemA
Dim converter As System.Componen tModel.TypeConv erter =
TypeDescriptor. GetConverter(my E)

In the immidiate window
? converter.ToStr ing() goves
"System.Compone ntModel.EnumCon verter"

whereas in my other project (also a strongly signed assembly, but referenced
directly from a newly created stub windows form project), I get

? converter.ToStr ing
"ClassLibrary1. LocalizedEnumCo nverter"

so it look like the LocalizedEnumCo nverter is not being bound to the enum -
any ideas? Is this because of the way Excel loads the assembly, and is there
a way arounfd this?