Monitoring a group of nodes

Hiya,

I'm not sure if I'm going about this the right way; what I want to do is monitor a group of nodes and fire an alert if a specified number of them go down.

So far I've created a group and added all of the nodes I want to monitor.  I'm setting the trigger condition to first check for the group name and then to check if the group member status is down.
I have also set the alert to be triggered if 5 or more objects have met the condition.

I have attached a screenshot below but I'm not sure if this is the best way to achieve what I want

Any help will be appreciated!

Thanks