Utilising Average Page Generation Time in Custom Alerts

Currently setting up Custom Alerts (V3.0.5), and looking to make use of the Average Generation Times for Pages - i.e. Alerting when a Page takes > 2s to generate.

I can’t seem to find any option to use this metric as a parameter in the Plugin - is this possible, or is there a different approach that can be taken in order to achieve the same goal?

Thanks in advance!