Delphi wwDbgrid,该怎么解决

Delphi wwDbgrid
wwDbGrid 批量修改？ 

 with wwDBGrid1,QDcCorrect do
    begin
      try
        DisableControls;
        for i := 0 to SelectedList.Count -1 do
        begin
          GotoBookmark(Pointer(SelectedList.items[i]));
          Active := True;
          Edit;
          FieldValues['Price_Unit_Qty'] := QDcCorrectPrice_Unit_Qty.Value; 
//只能修改一条记录？ 如何批量修改？赋值有问题。。？
          Post;
        end;
      except
        EnableControls;
      end;
    end;
   QDcCorrect.RefreshRecord;