动态更改WPF中的旋转动画

I am using a DoubleAnimation to anamiate the Angle property of a RotationTransform. Several times per second, I need to change the rate of the rotation in response to external data so that the rotation speeds up and/or slows down (smoothly) over time. I am currently doing this by using a DoubleAnimation that repeats forever from 0.0 to 360.0 with duration X, then several times per second:I am using a DoubleAnimation to anamiate the An