Try this code.
if (e.TableCellIdentity.TableCellType == GridTableCellType.RecordPlusMinusCell)
{
Record r = e.TableCellIdentity.DisplayElement.ParentRecord as Record;
if (r != null && r.NestedTables.Count > 0 && r.NestedTables[0].ChildTable.GetFilteredRecordCount() == 0)
{
e.Style.CellType = "Static";
e.Style.Borders.Bottom = new GridBorder(this.gridGroupingControl1.TableModel.Options.DefaultGridBorderStyle, SystemColors.GrayText);
}
}
Here is a sample.
http://www.syncfusion.com/Support/user/uploads/GGC_PasteSort_27ab40b7.zip