inputbox com mascara de cpf como fazer?

function TForm3.InputQuery(const ACaption, APrompt: string;
  var Value: string): Boolean;
  function GetAveCharSize(Canvas: TCanvas): TPoint;
var
  I: Integer;
  Buffer: array[0..51] of Char;
begin
  for I := 0 to 25 do Buffer[I] := Chr(I + Ord('A'));
  for I := 0 to 25 do Buffer[I + 26] := Chr(I + Ord('a'));
  GetTextExtentPoint(Canvas.Handle, Buffer, 52, TSize(Result));
  Result.X := Result.X div 52;
end;

var
  Form: TForm;
  Prompt: TLabel;
  Edit: TMaskEdit;
  DialogUnits: TPoint;
  ButtonTop, ButtonWidth, ButtonHeight: Integer;
begin
  Result := False;
  Form := TForm.Create(Application);
  with Form do
    try
      Canvas.Font := Font;
      DialogUnits := GetAveCharSize(Canvas);
      BorderStyle := bsDialog;
      Caption := ACaption;
      ClientWidth := MulDiv(180, DialogUnits.X, 4);
      ClientHeight := MulDiv(63, DialogUnits.Y, 8);
      Position := poScreenCenter;
      Prompt := TLabel.Create(Form);
      with Prompt do
      begin
        Parent := Form;
        AutoSize := True;
        Left := MulDiv(8, DialogUnits.X, 4);
        Top := MulDiv(8, DialogUnits.Y, 8);
        Caption := APrompt;
      end;
      Edit := TMaskEdit.Create(Form);
      with Edit do
      begin
        edit.EditMask:='999.999.999-99;0;_';
        Parent := Form;
        Left := Prompt.Left;
        Top := MulDiv(19, DialogUnits.Y, 8);
        Width := MulDiv(164, DialogUnits.X, 4);
        MaxLength := 255;
        SelectAll;
      end;
      ButtonTop := MulDiv(41, DialogUnits.Y, 8);
      ButtonWidth := MulDiv(50, DialogUnits.X, 4);
      ButtonHeight := MulDiv(14, DialogUnits.Y, 8);
      with TButton.Create(Form) do
      begin
        Parent := Form;
        Caption := 'Ok'; // AZ
        ModalResult := mrOk;
        Default := True;
        SetBounds(MulDiv(38, DialogUnits.X, 4), ButtonTop, ButtonWidth,
          ButtonHeight);
      end;
      with TButton.Create(Form) do
      begin
        Parent := Form;
        Caption := 'Cancelar'; // AZ
        ModalResult := mrCancel;
        Cancel := True;
        SetBounds(MulDiv(92, DialogUnits.X, 4), ButtonTop, ButtonWidth,
          ButtonHeight);
      end;
         if ShowModal = mrOk then
           begin
             Value:=Edit.Text;
             result:=true;
           end;
    finally
      Form.Free;
    end;
end;

procedure TForm3.Button4Click(Sender: TObject);
var
 Retorno:Boolean;
 Cpf:String;
begin
Retorno:=InputQuery('teste','Digite CPF',cpf);
  if Retorno then
    Showmessage(Cpf)
end;