Controlling event-driven navigation in a WPF application
For Each ThisControl In MainListView.
   Dim ThisControlType = ThisControl.GetType
   Dim ThisControlPropertyChangedEvent = ThisControlType.GetEvent("PropertyChanged")
   ' you might wanna check here if event is not null / nothing
   ThisControlPropertyChangedEvent.AddEventHandler(ThisControl, New PropertyChangedEventHandler(AddressOf APropChanged))
 Next

Public Sub APropChanged(ByVal sender As Object, ByVal e As PropertyChangedEventArgs)
If e.PropertyName = "Validated" Then
    Dim ValidatedForAll = True
    For Each ThisControl In MainListView.Items
        Dim ThisControlType = ThisControl.GetType
        Dim ThisControlValidatedProperty = ThisControlType.GetProperty("Validated")
        'you might wanna check for non null here
        If Not ThisControlValidatedProperty.GetValue(ThisControl, Nothing) Then
           ValidatedForAll = False
           Exit For
        End If
    Next
    If ValidatedForAll Then
       MessageBox.Show("Yeeppee")    ' you might send an event instead.
    End If
End If
End Sub