There is no such method publicly exposed so you can't. It depends on what you are trying to do as far as where you should try to override the default behavior. If you want to control the rendering and are using .NET 2.0 then the new OwnerDraw property and associated Draw event can be used to control how it renders the tool tip. If you want a notification when it occurs then you can handle the Popup event. Within the Popup event you can make some changes to the tooltip but I don't know how much you can actually do to control the rendering.
IExtender => ToolTip
jinath
Michael Taylor - 11/21/05