C++ Excel AddIn DLL that returns strings to C# and VBA

Question

I'm in the process of creating an Excel addIn package to work with a web service. I have a C++ .xll addIn that uses MSXML to communicate with the web service, and registers worksheet functions, but otherwise provides no UI.

I am developing a c# .net addIn to provide the GUI using the Office 2007 ribbon, and a VBA addIn for earlier versions of Excel.

Now a couple of the web service requests return string arrays, and I'm trying to find a way to make them compatible with both the VBA and C# addIns. (These are commands, not worksheet functions. Both C# and VBA can call the function through excel using Application.ExecuteExcel4Macro("FunctionName") )

Does anyone know how I can create a C++ DLL function that returns a string array that can be read by both a VBA addIn and a C# addIn?