TextChangeListener Between Two TextField

Hi Masters here:

I got two Textfields, a and b.
The value of b will be changed when user type something into a by registering a TextChangeListener.
Like,

a.addTextChangeListener(
new TextChangeListener()
{
private static final long serialVersionUID = 1L;
@Override
public void textChange(TextChangeEvent event)
{
b.setValue(event.getText() + “123”);
}
});

The next step is, how do I register a event for b, to let b know it has been changed itself to do the other jobs when above event has triggered?
Thanks a ton.

Probably add a ValueChangeListener?

Master, it worked by following your direction.
Thank you so much.