{ TDBGridEhSelectionRect }

function TDBGridEhSelectionRect.BoxRect(ALeft: Integer; ATop: TBookmarkStr;
  ARight: Integer; ABottom: TBookmarkStr): TRect;
var OldRec: Integer;
  TopGridBM, BottomGridBM: TBookmarkStr;
  TopRow, BottomRow: Integer;
  SwapCol: Integer;
  SwapBM: TBookmarkStr;

  function FindRecNumByBookmark(BM: TBookmarkStr): Integer;
  var i: Integer;
  begin
    Result := - 1 ;
    for i :=  0  to FGrid.FDataLink.RecordCount -  1  do
    begin
      FGrid.FDataLink.ActiveRecord := i;
      with FGrid.DataSource.DataSet do
        if CompareBookmarks(Pointer(BM), Pointer(Bookmark)) =  0  then
        begin
          Result := i;
          Break;
        end;
    end;
  end;
begin
  if ALeft > ARight then
  begin
    SwapCol := ALeft;
    ALeft := ARight;
    ARight := SwapCol;
  end;
  if FGrid.DataSource.DataSet.CompareBookmarks(Pointer(ATop), Pointer(ABottom)) >  0  then
  begin
    SwapBM := ATop;
    ATop := ABottom;
    ABottom := SwapBM;
  end;
  OldRec := FGrid.FDataLink.ActiveRecord;
  try
    FGrid.FDataLink.ActiveRecord :=  0 ;
    TopGridBM := FGrid.DataSource.DataSet.Bookmark;
    if FGrid.DataSource.DataSet.CompareBookmarks(Pointer(ATop), Pointer(TopGridBM)) <  0  then
      TopRow :=  0 
    else begin
      TopRow := FindRecNumByBookmark(ATop);
    end;
    if TopRow = - 1  then TopRow := FGrid.FDataLink.RecordCount;
    TopRow := TopRow + FGrid.TopDataOffset;

    FGrid.FDataLink.ActiveRecord := FGrid.FDataLink.RecordCount -  1 ;
    BottomGridBM := FGrid.DataSource.DataSet.Bookmark;

    if FGrid.DataSource.DataSet.CompareBookmarks(Pointer(ABottom), Pointer(BottomGridBM)) >  0  then
      BottomRow := FGrid.VisibleDataRowCount
    else begin
      BottomRow := FindRecNumByBookmark(ABottom);
    end;
    BottomRow := BottomRow + FGrid.TopDataOffset; // -  1 ;
  finally
    FGrid.FDataLink.ActiveRecord := OldRec;
  end;

  Result := FGrid.BoxRect(FGrid.DataToRawColumn(ALeft), TopRow,
    FGrid.DataToRawColumn(ARight), BottomRow);
//
end;

      СЫРЕЦ EHLiba

    if FGrid.DataSource.DataSet.CompareBookmarks(Pointer(ATop), Pointer(TopGridBM)) <  0  then

              begin
                if ssShift in Shift then
                  if Selection.SelectionType = gstRectangle then
                    Selection.Rect.Select(Cell.X - IndicatorOffset, DataSource.DataSet.Bookmark, True)
                  else
                  begin
                    Selection.Rect.Select(OldCol - IndicatorOffset, OldBM, False);
                    Selection.Rect.Select(Cell.X - IndicatorOffset, DataSource.DataSet.Bookmark, True);
                  end
                else
                  Selection.Rect.Select(Cell.X - IndicatorOffset, DataSource.DataSet.Bookmark, False);
                FDBGridEhState := dgsRectSelecting;
              end;