title: Issue with WPF Focus
body: <p>I have code that handles the LostFocus event of my controls.  It validates the value and in some cases will enable a subsequent control.  For instance, there might be a ComboBox that allows a user to select a country.  The subsequent ComboBox allows the user to select a state.  IF the currently selected country is not the USA, the state ComboBox is disabled.  If the user selects "USA" and then tabs out of the combo box, the LostFocus code enables the state ComboBox.  However, the State ComboBox does not get focus, instead focus goes to the control that follows the State ComboBox.</p>
  
  <p>I've tried using the PreviewLostKeyboardFocus to handle the event instead with no luck.  I'm kind of at a loss as to figuring out someway to hack WPF to get this work.  Any suggestions?</p>