Pressing F1, in the Visual Basic for Applications or Visual Basic Code Window, will not display the help topic for a target that is a coclass or class.
The default interface for the coclass or class is IUnknown. The majority of the coclasses and classes in ArcObjects have IUnknown as the default interface. If the target's default interface is not IUnknown, F1 Help will display the topic for the default interface.
In the Visual Basic Editor press F2 or the Object Browser icon.