I would make an animated progress bar which resets on reaching the end. Easiest would be to create two rectangles, one on top of antother with different colors. Animate width of the one on the top from 0 to length of your progress bar. You can control it by making a property which indicates how long should the animation last. And maybe some start method to synchronize with refresh actions.
EDIT. There is example on msdn HERE (examples section)