How to ignore duplicate request processing

<zk>
	<window style="padding: 25px;">
		<button label="Next" onClick="self.setDisabled(true);"/>
	</window>
</zk>

<zk>
	<zscript>
		import org.zkoss.zk.ui.util.GenericForwardComposer;
			
		public class myController extends GenericForwardComposer {
		
			public void onClickNext(Event event) {
				event.getOrigin().getTarget().setDisabled(true);
			}
		}		
	</zscript>
	<window style="padding: 25px;" apply="myController">
		<button label="Next" forward="onClick=onClickNext()"/>
	</window>
</zk>

	/**
	 * Opens the help screen for the current module.
	 * 
	 * @param event
	 * @throws InterruptedException
	 */
	private void doHelp(Event event) throws InterruptedException {

		FDMessageUtils.doShowNotImplementedMessage();

		// we stop the propagation of the event, because zk will call ALL events
		// with the same name in the namespace and 'btnHelp' is a standard
		// button in this application and can often appears.
		// Events.getRealOrigin((ForwardEvent) event).stopPropagation();
		event.stopPropagation();
	}