Force a WPF DataBinding to Update
From: http://blogs.msdn.com/jaimer/archive/2007/07/04/forcing-a-wpf-binding-to-refresh.aspx
Now I'll find it again, since it took me five minutes to find that link even after using it once.
BindingOperations.GetBindingExpressionBase(_dependencyObjectWithBinding, TextBlock.SomeDependencyProperty).UpdateTarget();