设置MKPolylineView lineDashPattern为动画

I have been trying to work on a application using the MapKit and MKPolyline. I have gotten the annotations and paths drawn on the map, however I am trying to change the lineDashPattern to be a set of animated dashes in the direction of the course. I know that the lineDashPhase and lineDashPattern together give you a dashed line, and the more you increase lineDashPhase, the more the dashes move, however is there a way to increase the values in such a way that it appears that it is moving, sort of like ants along a line I guess is a good analogy. I have been trying to work on a application usi