groupByDataLayer.refresh();
groupByModel.update();
natTable.doCommand(new VisualRefreshCommand());
groupByDataLayer.killCache();

            // we register a custom UpdateDataCommandHandler that ensures to
            // update the tree structure
            this.bodyDataLayer.unregisterCommandHandler(UpdateDataCommand.class);
            this.bodyDataLayer.registerCommandHandler(new UpdateDataCommandHandler(this.bodyDataLayer) {
                @SuppressWarnings("unchecked")
                @Override
                protected boolean doCommand(UpdateDataCommand command) {
                    if (super.doCommand(command)) {
                        T o = ((IRowDataProvider<T>) BodyLayerStack.this.bodyDataProvider).getRowObject(command.getRowPosition());
                        int rowIndex = BodyLayerStack.this.sortedList.indexOf(o);
                        if (rowIndex >= 0) {
                            BodyLayerStack.this.sortedList.set(rowIndex, o);
                        }
                        return true;
                    }
                    return false;
                }
            });

bodyDataLayer.registerCommandHandler(new ILayerCommandHandler() {

			@Override
			public Class getCommandClass() {
				return UpdateDataCommand.class;
			}

			@Override
			public boolean doCommand(ILayer targetLayer, final ILayerCommand cmd) {
				// some stuff to do the UpdateData goes here (actually, I'm using command and an EditingDomain here to support Undo/Redo, but that's not important...)
				
                                // test if we are really modifying data which requires a tree structure update
				if (groupByModel.getGroupByColumnIndexes().contains(((UpdateDataCommand)cmd).getColumnPosition())) {
                                        // read out the tree structure, clear it, rebuild it
					List<Integer> groups = new LinkedList<Integer>();
					groups.addAll(groupByModel.getGroupByColumnIndexes());
					groupByModel.clearGroupByColumnIndexes();
					for (Integer index: groups)
						groupByModel.addGroupByColumnIndex(index);
				}
				return true;
			}

		});