[Q] Lua trigger for change of posture - help

[Knightpawn]

I want to create an event where the action is 'Change Mission Status' and the trigger is side A becoming Hostile (it is unfriendly at start). I don't see an ready trigger for that nor an option to "lua script" a trigger. How would you do it?
Is it 'Scenario is loaded' as a trigger for an event and then in the lua script of the action that event one sets the above as a 'hidden event' ?

[Nikel]

Why side A becomes hostile?

[Knightpawn]

Because side A is player and he chooses the time to attack. (Player side becomes hostile for the computer player). Until then each side treats the other as unfriendly

[Nikel]

If the player is attacking, then is damaging or destroying the computer side units.

Those are valid triggers.

[Knightpawn]

If the player is attacking, then is damaging or destroying the computer side units.

Those are valid triggers.

You are right!