use a game logic. from tyger's script:
_parachute = "Parachute" camCreate [(_pos select 0) + 2,(_pos select 1) + 10, 175]
_parachute setdir random 360
_logic = "Logic" camCreate [0,0,0]
_logic moveInDriver _parachute
#ParaLoop
_parachute setVelocity [(velocity _parachute select 0) / 1.1, (velocity _parachute select 1) / 1.1, -6]
_ammobox setPos [getPos _logic select 0, getPos _logic select 1, (getPos _logic select 2) + 1]
_ammobox setdir getdir _logic
~0.01
? vehicle _logic != _logic : goto "ParaLoop"
_ammobox setPos [getPos _ammobox select 0, getPos _ammobox select 1, 0]
deleteVehicle _logic
works in ofp, untested in arma.