Create a parallel line in a perpendicular direction between two lines.

how to create a copy of a line parallel to another line and move down by 268 perpendicularly ?

I have a green line (3D alignment line) and a cyan line, I am trying to create the pink line. 

the perpendicular (normal) distance between pink line to green line is 268. 
pink line needs to follow the same 3D alignment (parallel) as the cyan line. 

Note: intersection between red dash line (normal line between green and cyan) and cyan line IS NOT at the midpoint of cyan line.