The ChildMouseEnter event occurs for a CompositeField when the mouse cursor enters one of its child fields. If no CompositeField is specified, the event occurs when the mouse cursor enters a field on the frame form.

ChildMouseEnter events do not occur when the mouse is captured (that is, during a drag-and-drop operation). If a ChildMouseEnter event occurs and the corresponding ChildMouseExit event has not occurred when the mouse is captured, a ChildMouseExit event will be generated when the mouse becomes captured. Thus, every ChildMouseEnter event is followed by a matching ChildMouseExit event. When a ChildMouseExit event is generated because the mouse becomes captured, the associated ReasonCode is RC_MOUSECAPTURED.