[Страдалецъ]

Где то так:

Код:

procedure TForm14.FileListBox1Change(Sender: TObject);
begin
 if FileListBox1.ItemIndex = -1 then Exit;
 Label1.Caption := FileListBox1.Items[FileListBox1.ItemIndex];
 try
 with TFileStream.Create(Label1.Caption, fmOpenRead)
 do begin
    Panel1.Caption := IntToStr(Size);
    Free;
    end;
 except
  Panel1.Caption := 'Locked';
 end;
end;