I'd suggest something like mezzy's sayings.
Off course, ya could specify the conditions a bit (so that it is the "gunner" and not the driver or passengers who drops the eggs).
Say, the m113 is named "M"
condition:
MG == player && (MD in MG) && (Damage M <= 0.6) && !(MD == player)
or alike...
the last part is to prevent the "manual fire" driver option from cheating, so that the vehicle DOES need at least two crew members.
uuuum, well... about the scroll, the activation, the laying....
I'd suggest an "addaction" like mezzy's, only the script itself could be much more simplified. Like if the "M" vehicle dropped a mine for each 5 seconds (or minutes or whatever) - yer choise!
And when the player hits the "deactivate" action button, the auto laying stops.
Or you could make the addaction a SINGLE-DROP-ACTION (SDA)
;D
That way, the action is fired, a mine is camCreated right behind the vehicle, and the action gets instantly removed (and pops up again right away). Then you hit the action button again, and yer vehicle drops yet another mine etc.
That would just take a very short scroll