[alquimista]

Por si sirve a alguien..

Para un listbox o u Treeview;

Código Delphi [-]
procedure TForm11.btn1DragDrop(Sender, Source: TObject; X, Y: Integer);

var a:string;
begin
if Source is TlistBox then

  begin
 (Sender as TButton).Caption :=
    (Source as TListBox).Items[(Source as TListBox).ItemIndex];
  end;
 if Source is TTreeview then
   (Sender as TButton).Caption :=
    (Source as TTreeView).Selected.Text;
end;