set property after animating it

Hello,

I'm running an animation on the OffsetX property of my TranslateTransform3D
object by setting by="-1" . after i run the animation, i want to make the
OffsetX some other value in my C# code. the problem is that after animating
the first time around i can set OffsetX but it obtains the value i set minus
1. the second time i run the animation i can't set the OffsetX at all. it
just has the old value after i set it. i tried calling stop() on the
storyboard that has the animation but that did nothing. what am i doing
wrong here?

thank you, amir