var
  s, path: string;
  i  : integer;
  stl : tstringlist;
begin
   path:=DirectoryDialog.Directory+'\*.*'#0;
   s := path;

   ListBox1.Perform(LB_DIR, DDL_READWRITE, LongInt(@s[1]));
   listbox1.ItemIndex:=0;

  stl:=tstringlist.Create;
  try
    for i := 0 to listbox1.items.count - 1 do
    begin
      stl.Add(listbox1.items.strings[listbox1.itemindex]);
      listbox1.ItemIndex:=listbox1.ItemIndex+1;
    end;
    listbox1.Items.CommaText:=stl.commatext;
  finally
    stl.Free;
  end;
end;