It only works against the AI, and can be a bit tedious but a good compromise is to set OPfire Confirm to "On". Then you can pick which targets to allow your AT (or any other unit) to fire against.

<t> Interesting at first glance, but not exactly rocket science:<br/>
<br/>
If x = first 3 #'s<br/>
y = last 4 #'s<br/>
<br/>
Then the instructions become: ((((x*80)+1)*250)+2*y-250)/2<br/>
<br/>
Simplify: x*40*250+y = x*10,000 +y<br/>
<br/>
Therefore, whatever 3 digit number you put in for ...