Wpf, doubleanimation on fontstretch property

Question

How to make an animation which changes FontStretch? This is what I've tried:

<Style TargetType="TextBlock" x:Key="TextBlockStyle">
  <Style.Triggers>
    <EventTrigger RoutedEvent="Button.MouseEnter">
      <EventTrigger.Actions>
        <BeginStoryboard>
          <Storyboard>
            <DoubleAnimation Storyboard.TargetProperty="FontStretch" To="UltraCondensed" Duration="0:0:0.3"/>