...
    q.DisableControls;
    if DBGridEh1.Selection.SelectionType = gstRecordBookmarks then
    begin
      for I :=  0  to DBGridEh1.Selection.Rows.Count -  1  do
      begin
        q.GotoBookmark(Pointer(DBGridEh1.Selection.Rows[I]));
// что-то делаем
      end;
      DBGridEh1.Selection.Rows.Clear;
    end
    else
    begin
// что-то делаем
    end;
  finally
    q.EnableControls;
  end;
...