[V8i VBA] Detecting if coordinate is above or below target element

As a followup to one of my previous threads here, the image below is is my target element (its 22miles long) with the placed cells also shown (very hard to see at this scale)

This is a close-up where the cells are visible and though difficult tell, they are placed perpendicular to the chainage element (turquoise):

I now have a requirement to add text (possibly a text node) near to each cell instance which where each string would be unique like below:

I have 2 issues (a far as I can tell),

1. I do not know how I can detect if a coordinate is south of the chainage line at its projected intersection perpendicular to the chainage element.
2. I can't store the text in a cell (even though it does make the most sense) because any cells inserted south of the chainage element would have the text rotated 180° whereas I need to text to be readable in the same direction as above.

Any suggestions how I can achieve the above?