You have to call the event in the monthly country pulse. It is not a trigger 
You'll find those in game/common/on_actions
You should also be aware that such events/effects are called on every country.
Additionally, this is not valid syntax:
I'd recommend having a browse through the use of variables in vanilla events/on_actions.
You'll find those in game/common/on_actions
You should also be aware that such events/effects are called on every country.
Additionally, this is not valid syntax:
Code:
random_number = { 0 1 }
add_religious_power = random_number