Calculating avg distance between two non-parallet lines?

I'm currently working on creating a data model that will allow the analyst to digitize two non-parallel lines of approximately the same length. Currently the methodology is to divide the lines into 11 points and avg the distances between the two lines.

Any suggestions on how to simplify this method and or automate the process, remember I'm creating the schema so I have full range to change what is and how it is being recorded?

Attached is an example of the problem.