[alquimista]

Bueno ya se lo que me pasaba, pensaba que era automatico y no me salia el drag and drop.
Tenia que poner en el listbox la propiedad Dragmode:=dmautomatic;
y el evento dragover.
Pensaba que era mas dificil.

Código Delphi [-]
procedure TForm11.btn1DragDrop(Sender, Source: TObject; X, Y: Integer);
begin
 (Sender as TButton).Caption :=
    (Source as TListBox).Items
    [(Source as TListBox).ItemIndex]
end;

procedure TForm11.btn1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
   Accept := True;
end;