Editing Datagroup properties with VBA

HAving re-registered the AutomationInstanceData.dll file I can now read all my datagroup properties for each element in a file. but this is a read only function.

How can I change the value of a datagroup property using VBA ?

e.g I want to change the Wall Finish of a Space to "Plaster".

There does not seem to be a way to write back a value to a datagoup property item ? 

I have several thousand spaces that I want to be able to maintain externally via an excel spreadsheet.

 Can anyone help ?

Thanks Stephen