AutoCAD Civil 3D :: Assembly Based On End Condition (not Start Condition)

I am using Civil3D 2011 and have a need to create an assembly that will take one of three options, depending on the tie-in condition points (e.g., the end of a link, not the beginning). As far as I can tell, Civil3D can discriminate which sub-assembly to choose based on conditions at the link starting point (e.g., if the start point is 2' of fill, it will select sub-assembly A; if the start point is 2' of cut, it will use sub-assembly B, etc.). However, I have a condition where the cut/fill conditions at the assembly start point have little to do with what I want the subsequen sub-assembly to do.

For simplicity's sake, you can imagine my "existing conditions" (2D) section as a flat-bottomed, U-shape with vertical sides (i.e., a trench); it's bottom width can vary.For the time-being, let us consider one side of an assembly in a fill condition only. Imagine that I want to satisfy design constraints but limiting fill quantities is a second priority; in instances when the bottom width is small, I would want the assembly to catch the existing trench with a 2:1 sideslope fill (or in Civil3D speak, a cut, because it would be upwards), so my finished surface is a now a V with the vertical faces above it. That works fine and dandy for a "trench" a few feet wide; however, imagine if that trench were 100s of feet wide - a 2:1 side slope would be a lot of fill for a ditch. So rather, I would want to "embank" the ditch - 2:1 side slope up (cut) to define my ditch XS, a horizontal link over to "embank" it, and then a 2:1 side slope down (fill) to catch the flat-bottom of my trench. So as you see, both situations have the same "Cut/Fill" condition (starting point) but drastically different end results.