HeelX: This line won't even compile - lists are only possible for array definitions. Look in the manual DLL interface chapter for the correct syntax to define a GUID. You had it already right in your previous example. You can also find an example in the pictures.h header as Tobias suggested, and use that as a template.

A GUID is a 16-byte sequence that you use for uniquely identifying a COM interface. You use it for example when you create an instance of that interface.