Well you know how when you run a script, say from a trigger, you put something like
[var1,var2,...] exec "scriptname"
in the activation field of a the trigger. Well instead of putting it in the trigger put exactly the same in the code of the first script. That way the first script will then run the second script.
In your example I would not do it that way. What I suggest is you set a trigger that fires when the chopper is where you want it to start the drop. Get that trigger to run the following script
_delay = 10
[mygrp,heli1] exec "groupeject.sqs"
~ _delay
[othergrp,heli1] exec "groupeject.sqs"
exit
and then just play with the value for _delay