Wall Template (SS2)

I have a situation where I need to place a wall of varying height along a roadway and I'm stumped as how to make it work.

The image attached shows what I need. I can use a wall template that is the same height throughout the run which would be no problem but I need it to vary depending on the slope and height of the grade behind it. What type of constraints would I use? Is there a magical template that is available somewhere on the web that I can steal?