How to Reverse an animation (execute it in reverse) via pure xaml

I made an animation OpenMenuzin Storyboard and so on, I already did this before reversing the animation by C #

//pode estar errado mas foi mais ou menos isso
sb = (Storyboard)Resources["Animaçao"];
sb.AutoReverse = true;
sb.Begin();
sb.Seek(TimeSpan(0, 0, 0), TimeSeekOrigin.Duration);

This works + - but it should be used, but how do I do this animation to reverse (reverse) the pure xaml.

Where I Left:

<EventTrigger RoutedEvent="Expander.Collapsed">
<SeekStoryboard BeginStoryboardName="AbrirMenuzin" Offset="0" Origin="BeginTime"/>
</EventTrigger>

Ps: I do not want to duplicate / create another storyboard, but only reverse the existing storyboard.