public void onEvent(Event event) {
listCostCategories.renderAll();
final Rows rows = listCostCategories.getRows();
for (Iterator i = rows.getChildren().iterator(); i.hasNext(); ) {
final Row row = (Row) i.next();
final CostCategory category = (CostCategory) row.getValue();
Button btnDelete = (Button) ((Hbox)row.getChildren().get(2)).getChildren().get(1);
if (!canRemoveCostCategory(category)) {
btnDelete.setDisabled(true);
btnDelete.setImage("/common/img/ico_borrar_out.png");
btnDelete.setHoverImage("/common/img/ico_borrar_out.png");
}