public static readonly DependencyProperty ValueProperty =
    DependencyProperty.Register(
        "Value", typeof(decimal), typeof(NumericUpDown),
        new FrameworkPropertyMetadata(MinValue, new PropertyChangedCallback(OnValueChanged),
                                      new CoerceValueCallback(CoerceValue)));

private static object CoerceValue(DependencyObject element, object value)
{
    decimal newValue = (decimal)value;

    newValue = Math.Max(MinValue, Math.Min(MaxValue, newValue));

    return newValue;
}

private static void OnValueChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
    NumericUpDown control = (NumericUpDown)obj;

    RoutedPropertyChangedEventArgs<decimal> e = new RoutedPropertyChangedEventArgs<decimal>(
        (decimal)args.OldValue, (decimal)args.NewValue, ValueChangedEvent);
    control.OnValueChanged(e);
}