IButton button = new IButton("Multilevel Sort");
button.setIcon("crystal/16/actions/sort_incr.png");
button.setWidth(120);
button.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
MultiSortDialog.askForSort(listGrid, listGrid.getSort(), new MultiSortCallback() {
public void execute(SortSpecifier[] sortLevels) {
//if sortLevels is null, it means that the Cancel button was clicked
//in which case we simply want to dismiss the dialog
if(sortLevels != null) {
listGrid.setSort(sortLevels);