I can't answer that question, but why would you do that? Right clicking usually causes the firing unit to stop firing and following the targeted unit once it leaves it's range. I don't like my indirect fire units suddenly appearing at the front line.
Because of :
1) Order to Shell Enemys Who are clumped up in Green Cover and Not the squad Who is spread out in the open
2) Focus prio targets (flamers, mgs, Elite infantry etc )
If I just let my arty Auto fire it's was to much random for me
The point with following is True but i got Used to Focus fire with multiple squads and then Press "stop". They will still Focus the same squad but wont follow them if they leave ur fire range.