Reported when the user attempts to drag an item from a tree which has the ‘DragSource’ property set to ‘true’. The message gives the selitems in force at the point when the drag begins – you may reject the message if it is not appropriate to drag this particular item, or you can re-assign ¾ to place your own information here. This ‘token’ will be passed to any potential drop-targets in the DRAGOVER and DRAGDROP messages which will be sent to the targets when required.