Не обновляются данные в DBGrid'e?

procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
 if DBGrid1.DataSource.DataSet.FieldByName('IDENT').Value='0' then
    with DBGrid1.Canvas do
    begin
      If gdSelected in State Then
        Brush.Color := clLime
      else
        Brush.Color := clYellow;
      Font.Color := clBlack;
      FillRect(Rect);
      TextOut(Rect.Left + 2, Rect.Top + 2, Column.Field.Text);
    end;
 
 if DBGrid1.DataSource.DataSet.FieldByName('IDENT').Value='1' then
    with DBGrid1.Canvas do
    begin
      If gdSelected in State Then
        Brush.Color := clSkyBlue
      else
        Brush.Color := clSilver;
      Font.Color := clBlack;
      FillRect(Rect);
      TextOut(Rect.Left + 2, Rect.Top + 2, Column.Field.Text);
    end;
  if DBGrid1.DataSource.DataSet.FieldByName('IDENT').Value='12' then
   with DBGrid1.Canvas do
    begin
      If gdSelected in State Then
        Brush.Color := clLime
      else
        Brush.Color := clRED;
      Font.Color := clBlack;
      FillRect(Rect);
      TextOut(Rect.Left + 2, Rect.Top + 2, Column.Field.Text);
    end;
end;
      dm.Poisk_N.Close;
       if dm.T_Poisk.Active then dm.T_Poisk.Rollback;
      dm.Poisk_N.ParamByName('NZAP').AsInteger := strtoint(label4.Caption);
      dm.Poisk_N.Open;
 Form1.DBGrid1.DataSource:= dm.Poi_N_Source;