Retrieves a value that identifies the part of a rendering behavior on which this event was fired.
HRESULT value = object.get_behaviorPart(long* p);
the behavior part identifier.
The IHTMLEventObj3::behaviorPart property is only applicable for rendering behaviors that implement hit testing.
The IHTMLEventObj3::behaviorPart property is set by the IHTMLPainter::HitTestPoint method when an event fires on a rendering behavior. It is a custom property that a rendering behavior can use to identify a specific part of the element that caused the event to be fired.