Change state event - update WorkItem

Hi,

I would like to change some attribute after a chenge state event.
I created a new plu-in
<xml>
<eclipse>
<plugin>
<extension>
<operationParticipant>
<extensionService>
<prerequisites>
<requiredService>
<requiredService>
<requiredService>
</prerequisites>

</extensionService>
</operationParticipant>
</extension>
<extension>
<eventHandler>
<extensionService>
<prerequisites>
<requiredService>
<requiredService>
<requiredService>
</prerequisites>
</extensionService>
</eventHandler>
</extension>

</plugin>

and a class Evento
public class Evento extends AbstractService implements IChangeEventHandler {
private IProcessConfigurationElement fConfigurationElement;
private IProjectArea fProjectArea;
private IProcessArea fProcessArea;


@Override
public void handleEvent(IChangeEvent event,
IProcessConfigurationElement handlerConfiguration)
throws TeamRepositoryException {
// TODO Auto-generated method stub

fProcessArea = (IProcessArea) event.getProcessArea();

IRepositoryItemService repoService = super.getService(IRepositoryItemService.class);
fProjectArea = (IProjectArea) repoService.fetchItem(fProcessArea.getProjectArea(), IRepositoryItemService.COMPLETE);
IAuditable auditable = ((ISaveParameter) event).getNewState();
IWorkItem workItem = (IWorkItem) auditable;
String summary = workItem.getHTMLSummary().getPlainText();
if(summary.contains("te")) {
IWorkItemServer service= getService(IWorkItemServer.class);

workItem.setHTMLSummary(XMLString.createFromPlainText("Example work item"));
service.saveWorkItem2(workItem, null, null );



}

}}


but don't work.

Any suggestion??