In need of a report that shows the span of time when an alert is triggered and when its acknowledged.

We are looking to implement some Operational Level Agreements within our NOC regarding the time it takes to acknowledge an alert once it has been triggered. As the question states I'm looking for a report which would illustrate the time delta for all triggered alerts and when they were acknowledged. For example CPU alert was triggered at 9:00am and acknowledged at 9:10am.

Thanks,

MC