You can find some ways to trace flow shown in Demo/Graphs/PathFinding and in CustomDraw examples. If you prefer moving a node along the path, you could call InternalUtils.PointAlongLength to find position for the node, where distance argument is between 0 and DiagramLink.Length. For second 'segments' argument, try using result of this function when the link is Bezier -

PointF[] ConvertToPolyline(DiagramLink link)
{
	using (var path = new GraphicsPath())
	{
		float maxDist = 0.75f * Constants.GetMillimeter(link.MeasureUnit);
		path.AddBeziers(link.Points.GetArray());
		path.Flatten(Constants.IdentityMatrix, maxDist);
		return path.PathPoints;
	}
} 

Regards,
Slavcho
Mindfusion