private static void valuetachanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ValueNodeControl Target = d as ValueNodeControl;
            bool             NewVal = (bool)e.NewValue;

            if (NewVal)
            {
                Target.valut.Visibility = Visibility.Visible;
            }
            else
            {
                Target.valut.Visibility = Visibility.Collapsed;
            }
        }
        private static void internalvalChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            //the internal value has changed, we need to update our control
            ValueNodeControl Target = d as ValueNodeControl;
            double           Nieuw  = (double)e.NewValue;

            //a minus must become before a symbol
            if (Nieuw < 0)
            {
                Target.digits.Content      = Math.Abs(Nieuw);
                Target.Negative.Visibility = Visibility.Visible;
            }
            else
            {
                Target.digits.Content      = Nieuw;
                Target.Negative.Visibility = Visibility.Collapsed;
            }
        }