IF THEN ELSE - How to do that?

I am totally new to modding, so know about nothing at all:-)

My sim has a bad habit to go out, no matter the weather to talk to a plant, remove garbage or whatever, no matter the weather! So in the middle of thunderstorms with lightning striking near the house, he still decided to go out, several times and run in again.

That made me thinking of a mod that should stop a sim in wanting to go out if the lightning strikes.

I have found a three lines in tuning with the word lightning but can not find any line about walking out while lightning.

Is there a way to make a behavior dependent on an other?

IF lightning

THEN stay inside you idi*t

ELSE just go out