Pausing and resuming a storyboard with triggers

   
     
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      HorizontalAlignment="Center" VerticalAlignment="Center">
        
        <Ellipse Name="myEllipse" Fill="Red" Height="100" Width="10">
          <Ellipse.Triggers>
            <EventTrigger RoutedEvent="Ellipse.MouseEnter">
              <BeginStoryboard Name="changeWidth">
                <Storyboard>
                  <DoubleAnimation Storyboard.TargetProperty="(Ellipse.Width)"
                                   To="300" Duration="0:0:5" />
                </Storyboard>
              </BeginStoryboard>
            </EventTrigger>

          </Ellipse.Triggers>
        </Ellipse>
</Page>