In case it's launched by a player and not by a command you could check out this from the aciton sticky thread:
Name: Scud launch preparation
Description: Makes scud missile move to vertical ready-to-launch position
Syntax: unitname action ["scud launch"]
Example: scud1 action ["scud launch"]
Note1: Takes about 12 seconds
Note2: Use the command scudstate to check the launch state of the scud
Name: Scud start
Description: Makes scud missile ignite and launch
Syntax: unitname action ["scud start"]
Example: scud1 action ["scud start"]
Note1: You do not have to use the action Scud launch first
Note2: Use the command scudstate to check the launch state of the scud
Look at the note 2s.
If the scudstate is 0 then nothing has happened.
If it is 1 then the rocket has been errected.
It it is 2 then the rocket is ready to fire.
If it is 3< then the scud has been fired.
So you could have
#Check
?(scudsate scud>3) : goto "Launched"
~1
goto "check"
#Launcher
Guy Say "OhNo"
exit
The numbers for the states are a little wobberly though so you may need to experiment.