CONNECT 2 POINTS FOLLOWING CONTOURS

[RleeXD40]

I am working on a flood inundation, I would like to find a lisp or command(i'm not finding) to connect two points with a given elevation following the surface file or surface entities. 

here is a small section as example right now it's just guesswork, some of these have taken a week to connect all the sections.

[Patchy]

You could ask the Customization Group or if you have C3D, ask that group to see if they know how.

[mathewkol]

I assume A and B are the same elevation? Easy to do with Civil 3D if you have access to it. It's called a user-defined contour. If you don't have C3D, like you thought, you'll need. 3rd party app.