Change absolute layout with animation

How can I change absolute layout parameters with animation, like if a want to change the width of this:

mainLayout.Children.Add(someButton);
AbsoluteLayout.SetLayoutFlags (someButton, AbsoluteLayoutFlags.All);
AbsoluteLayout.SetLayoutBounds (someButton, new Rectangle(1.0, 0.4, 0.2, 0.14));

I can't figure out how to reach the width property like if I change a control:

someButtonAnimation.Add (0, 1, new Animation (d => someButton.WidthRequest = d, 100, 200, Easing.SinInOut));