final ListBox choice = new ListBox();
choice.addItem( constants.UseRealDateAndTime() );
choice.addItem( constants.UseASimulatedDateAndTime() );
choice.setSelectedIndex( (executionTrace.getScenarioSimulatedDate() == null) ? 0 : 1 );
choice.addChangeHandler( new ChangeHandler() {
public void onChange(ChangeEvent event) {
if ( choice.getSelectedIndex() == 0 ) {
simulDatePanel.setVisible( false );
executionTrace.setScenarioSimulatedDate( null );