I wrote an airburst artillery script a while back for a mission I never released (or finished
).
What I did was create the artillery around the player's position, with a 'dead zone' around the player.
I was using what macca suggested, however instead of grenades I was using "Shell73" and "HEAT125".
The heat has less of an effective range, so I let those bursts get within 10m of the player. The shells were a lot nastier, and needed to be at least 25m clear of the player to not hurt them.
I've got the script here... but it's not very user friendly
I can post it up anyway and try to comment it if you'd like...
Gawd... I wrote it so long ago I can barely remember what I was trying to do ;D