Can you get the final value from an animation before that animation has completed?

Question

Say I start a four-second DoubleAnimation on the Canvas.Left property of a control that animates the value from its current value to 100 and that animation was started by calling BeginAnimation on that control in code-behind.

void Animate(Control someControlOnCanvas, int newX){

    var canvasLeftAnimation = new DoubleAnimation();
    canvasLeftAnimation.To = newX;
    canvasLeftAnimation.FillBehavior = FillBehavior.Stop;
    canvasLeftAnimation.Duration = new Duration(TimeSpan.FromSeconds(4));
    canvasLeftAnimation.Completed += (s, e) => {
        Canvas.SetLeft(targetButton, x);
    };

    someControlOnCanvas.BeginAnimation(Canvas.LeftProperty, canvasLeftAnimation);
}

Animate(somethingToMove, 100);

Say half-way through that animation--at the two-second mark--I need to cancel the current animation and start a new one with a new To position (the From position would be wherever it is right now) that's 100 past where the first animation would end (i.e. not where it currently is at 50, but where it's supposed to be, which is 100, so adding another 100 would yield a new target of 200.)

If I try getting the current Left value, it's the animated value of 50. If I try getting the base value, it's where the animation started, which is zero since it's not officially updated until the completion handler fires.

So outside of manually adding a variable to track where things should be, how can I start a new animation that says 'Go to the original end, plus 100?'

My thoughts are:

1. Get the existing/current animation
2. Get it's To value
3. Start a new animation with the previous animation's To value, plus 100

What I'm stuck on is getting #1.

...or am I going about this all wrong?