Got home, got manual, got disappointed!

[Chazar]

Well, in addition, when I asked about a formula, I was rather referring to the mechanics used to determine the divergence from the target square, not for a closed formula...

I assume that the "mechanics" might be something like for every square that the projectile flies, there is a chance based on weather (strom/rain/snow), precision and basic weapon range whether the projectile goes astray from its designated course a bit...

But leaving this aside, my real problem is that I'm still lacking a feel for precision-values in relation to range, especially when it comes to mages that won't shoot they lightning bolts in such a mass like archers. It just seems to me that scripting spells that affect only a single square is almost useless without wind-guide, aim, eye of precision, etc. against foes that are not packed densely on the field...