AutoCAD .NET :: Get Distance Along Polyline

I am trying to get the distance of multiple block insertions that fall along a polyline to the startpoint/endpoint of said polyline.I can do this pretty easily using straight line (as the crow flies) distances between the block insertion and the polyline startpoint/endpoint, but I need the code to actually follow the polyline whenever it changes angle.

Is this possible using .NET?  How to start it?Below is my code to to get the straight line distance between the polyline startpoint and block insertion point:

Dim dist As Double = Math.Sqrt((acPline.StartPoint.X - acBref.Position.X) * (acPline.StartPoint.X - acBref.Position.X) + (acPline.StartPoint.Y - acBref.Position.Y) * (acPline.StartPoint.Y - acBref.Position.Y))