Nick

The important bits of the simplified code is as crude as follows. I removed
pretty much everything during my attempts to isolate the problem.

.....
using Extensibility;

[ClassInterface(ClassInterfaceType.AutoDual)]
public class I4XLFunctionLibrary : Extensibility.IDTExtensibility2
{

.....

public object I4XLQueryValue(string queryRef)
{
m_excelApp.Volatile(Type.Missing);
return "ABC";
}

I'm don't think that it will mak a dfference but the add-in is registered by
adding a Key to the registry under
HKLM\Software\Microsoft\Office\Excel\Addins and providing values for
Description, FriendlyName and importantly LoadBehavior=3



"Niek Otten" wrote:

What's the code of your UDF and how exactly do you call it? With what values?

--
Kind regards,

Niek Otten
Microsoft MVP - Excel

"Andrew Wiles" wrote in message ...
|I have an automation add-in which works fine on my UK English configuration.
| If I change the regional language settings in the control panel to Danish the
| UDF fails and returns #VALUE!.
|
| I have simplified this problem down to the point where the UDF is simply
| returning a string so the problem cannot (I think) be in the UDF processing.
|
| I am somewhat stumped as to where to go to resolve this problem.
|
| Any thoughts?
|
| Configuration is Excel 2007 on Vista x64