title: Can I force update of a Control via EventTrigger to another databound Control's "LostFocus" event?
body: <p>I have a <code>Person</code> class which does not implement <code>INotifyPropertyChanged</code>. My ViewModel has a property of type <code>Person</code>. In my View, one of the panels has <code>MyViewModel.SelectedPerson</code> as <code>DataContext</code>, so I bind some <code>TextBox</code>es to <code>Weight</code>, <code>Height</code> and <code>BodyMassIndex</code> properties.</p>
  
  <p>It so happens that <code>BodyMassIndex</code> is calculated from <code>Weight</code> and <code>Height</code>, but since <code>Person</code> doesn't notify its own changes, everytime I edit one of <code>Height</code> or <code>Weight</code>, <code>BodyMassIndex</code> doesn't update.</p>
  
  <p>My question is: How could I request a "refresh" of <code>textboxBodyMassIndex</code> Text property using an EventTrigger (or any appropriate other way) which "listens" to the other two textboxes "ValueChanged" event?</p>
  
  <p>Thanks for reading!</p>