I'm trying to create an automation that prevents the closure of an Epic, if all of its Stories are not closed. I've been following this post Stop Epic from closing if unresolved stories/tasks but I am not sure how to go back and call the Epic ticket's custom field to update it, once all the stories are closed.
I have it so that the automation checks to the epic to ensure it has a story, that has transitioned to done, where it then adds a value to the custom field. Now I need to set it so that, once all the fields have a value of 1 or once all the statuses are set to done, it then allows the Epic to close.

I'm not looking to add an app if at all possible.
Thanks!