How many ammo crates are you talking about? If it's relatively few, you could use
objStatus to hide / reveal pre-written lines.
(NB. I'm writing this as though it were for OFP - I hope it works the same for ArmA)
1. Edit the
briefing.html<p><a name="OBJ_10"></a>
Destroy as many ammo crates as possible.
</p><hr>
<p><a name="OBJ_11"></a>
Destroy as many ammo crates as possible. 10% destroyed.
</p><hr>
<p><a name="OBJ_12"></a>
Destroy as many ammo crates as possible. 20% destroyed.
</p><hr>
... etc.
2. In
init.sqs put all the crates in an array and hide the unnecessary objectives:
CrateList = [crate1, crate2, ... etc. ]
"11" objStatus "HIDDEN"
"12" objStatus "HIDDEN"
... etc.
3. Create an equal amount of triggers (triggered Once) to crates, and name them: oneCrate, twoCrates, etc. For
oneCrate:
condition: ({!alive _x} count CrateList == 1)
Activation: "10" objStatus "Hidden"; "11" objStatus "Active"; deleteVehicle oneCrate
then for
twoCrates,
condition: ({!alive _x} count CrateList == 2)
Activation: "10" objStatus "Hidden"; "11" objStatus "Hidden"; "12" objStatus "Active"; deleteVehicle twoCrates
and so on.
Obvious, stage 3 could be replaced by a script if you prefer.