You should call this method whenever one of the UIElementEvents (Enter/Leave) occurs for a UI element that must be handled by your code, that is, the C1DynamicHelp control cannot monitor this UI element for Enter/Leave events automatically (because it does not have those events). By calling this method you notify C1DynamicHelp that an event has occurred, so C1DynamicHelp can show the topic associated with that UI element. Typical usage is to override the ActivateUIElement(object) method, subscribing there to some events that would help you to detect the moments the focus enters/leaves the UI elements, and call HandleUIElementEvent method from those event handlers. In the HandleUIElementEvent call, the sender parameter is the UI element for which an event occurred, and uiElementEvent is the type of the event (Enter or Leave).