Centerline Curve Between Two Curves

Question

Hey all, 
 Usually I can find an answer to a question somewhere in the interwebs, but I can't seem to find one for this. I'm officially stumped. I look to you. 
 Is there a function within MicroStation (V8i SS2/3) that will show/draw the centerline between two curves, whether they be curves of straight lines, arcs, splines, or a combination thereof, whether 2D or 3D? 
 (Essentially, what's shown here http://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/creating-a-centerline-alignment-between-two-horizontal-alignments.aspx -- but with MicroStation. Not InRoads.) 
 Picture a creek, or a highway where the width of the median may vary, or something like those. I want to be able to pick the shoreline or edge of the highway and automatically get the centerline of said creek or median. 
 Such a thing seems possible in my head or on paper, but on the screen? Any ideas? 
 Thanks!

Carl Myhill · Accepted Answer

Another alternative - 
 1. Draw a construction line ( Yellow lines ) that connects at the ends of the curb lines 
 
 2. Use the 'Sweep Surface Along Curves' tool to generate surface ( tool settings : ' Sweep One along 2 or 3 ' / ' Arc Length' / ' Keep Path ' ) 
 
 3. Use the ' Extract Iso-Curves ' tool to obtain the center line by clicking on the surface and snapping to the mid point of the yellow construction line. 
 4. Delete the surface (unless required) 
 
 Note: The center line in the above example may not be based on the point of perpendicular / tangency to the outside lines required.