Is there a way to check the hex ID my creature is about to stand for the melee attack (if I click my mouse)?

Here's a problem I encounter. I try to make the Backstab ability, which gives a 20% bonus on the final damage if attacking from behind. The problem is, without a way to check the hex ID of my creature is about to stand for its next attack, I can't have the corrected damage shown on the screen (so it won't be like Cavalier with Charge ability, showing different damage according to mouse position).

Well, it's confusing to describe, let's see the code.


What should I change the MM:D line, for it to return the position my creature about to appear for the next attack?
In a word, is it possible to have my theoretical damage corrected depending on whether it's going to be an attack from behind?

I know it can be done by CM:A and a lot of lines. I hope to know an internal way so the code can be shorter.