DataBrowserItemDragRgnProcPtr

DataBrowserItemDragRgnProcPtr
Header:	ControlDefinitions.h		Carbon status:	Under Evaluation

typedef void(* DataBrowserItemDragRgnProcPtr) (
    ControlRef browser, 
    DataBrowserItemID itemID, 
    DataBrowserPropertyID property, 
    const Rect *theRect, 
    RgnHandle dragRgn
);

You would declare your function like this if you were to name it MyDataBrowserItemDragRgnCallback:

void MyDataBrowserItemDragRgnCallback (
    ControlRef browser, 
    DataBrowserItemID itemID, 
    DataBrowserPropertyID property, 
    const Rect *theRect, 
    RgnHandle dragRgn
);