Which member node is down in group alert?

I have a series of groups each containing four nodes. There two scenarios that I need to alert on. First, all member nodes down. Easy Peasy. The other is that one, two or three member nodes go down. Again, this is easy to alert on. The trick is identify which member nodes go down in the second scenario. Is there some variable I can use? Or, does anyone have a better idea to do what I am trying to do?

Thanks