Trigger help....visiblity enable/disable

Ok, it's easy enough to make a trigger that creates and enables a visibility modifier on a location, but I want to be able to disable/enable an already existing one...there's 'last created', but what if its not the last created modifier? how can I assign a visibility mod something specific?

As you create the visibility modifiers, set each one to a Visibility Modifier variable via "last created visibility modifier". You can refer back to them later this way.

Thanks. Seems a bit roundabout way to do it, but if thats the way it works :)