The following example copies the selected rows in a db grid to a list box.

procedure TForm1.Button1Click(Sender: TObject);
var
  i, j: Integer;
  s: string;
begin
  if DBGrid1.SelectedRows.Count> 0  then
    with DBGrid1.DataSource.DataSet do
      for i:= 0  to DBGrid1.SelectedRows.Count- 1  do
      begin
        GotoBookmark(pointer(DBGrid1.SelectedRows.Items[i]));
        for j :=  0  to FieldCount- 1  do
        begin

          if (j> 0 ) then s:=s+', ';
          s:=s+Fields[j].AsString;
        end;
        Listbox1.Items.Add(s);
        s:= '';
      end;
end;