Stop sending (duplicate) notification if alert is Active

I have an alert rule which monitor filesystem used for all of the hosts in our server farm and windows drives on those host. I want to stop sending repeat notification if an Alert/Warning is active for a specific host and drive combination.

As you can see in image, I have a warning and alert threshold condition. I want to send Warning message only once e.g. if C:/ on host01 breaches threshold of 80% and then Alert, also once, if it breeches 90% filesystem used.

How should I approach this? Any pointer is appreciated.
Thanks in advance.

image