An event which is raised when the XLL is opened.
class CXllOpenEvent : public CXlEvent
The event occurs when the XLL is opened, after CXllApp::OnXllOpenEx().
Observers should register for this event early in the life of the XLL. Registration can be done explicitly during CXllApp::InitInstance, or automatically by creating an instance of CXllOpenEventStaticObserver.
When observers are notified, an argument of type CXllOpenEventArgs is passed.