Add Ajax update behavior in Loadable detachable component

Hi,

The scenario is that i have a label "STATE", which has a loadable detachable
model.
Now when the content(text) of this label gets updated i want to update
another Label "Performed By" .

final IModel<String> performedByUserModel = Model.of("NA");
final Label performedByUser = new Label("performedByUser",
performedByUserModel);
// I need to update performedByUserModel to say "USER NAME" , when
below state gets updated.

performedByUser.setOutputMarkupId(true);
form.add(performedByUser);

IModel<String> stateModel = new LoadableDetachableModel<String>() {

private static final long serialVersionUID = 1L;

@Override
protected String load() {

return labTestService.getCurrentState(category,
labTest).getValue();

};

final Label state = new Label("currentState", stateModel);
state.setOutputMarkupId(true);
form.add(state);

Pls help how can i achieve this? How can i invoke an ajax call from state .
I am not able to add Ajaxbehavior to state here:
* state.add(new AjaxFormChoiceComponentUpdatingBehavior() {
* private static final long serialVersionUID = 1L;
* @Override
* protected void onUpdate(AjaxRequestTarget target) {
* performedByUserModel.setObject("User Name");
* target.add(performedByUser);
* }

Adding behavior like above throws a wicket exception "behavior can be added
to instance of FormComponent.,