Disabling a EventTriggerStoryboard Dynamically

<Grid.Triggers>
    <EventTrigger RoutedEvent="Border.Loaded">
            <EventTrigger.Actions >
                    <BeginStoryboard>
                            <Storyboard x:Name="MyStoryboard"    AutoReverse="True" RepeatBehavior="Forever">
                                  <ColorAnimationUsingKeyFrames    BeginTime="00:00:00"  Storyboard.TargetName="border" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)">
                                       <SplineColorKeyFrame KeyTime="00:00:01" Value="#FFFAFAFA"/>
                                  </ColorAnimationUsingKeyFrames>
                            </Storyboard>
                    </BeginStoryboard>
            </EventTrigger.Actions>
    </EventTrigger>
</Grid.Triggers>