How to add calculations in field override


I am trying to use the field override with value mapping in grafana.

I am fetching few records from elastic ,it has a column with time value, if the time value is old (for example, if the current time is 7:33 PM and the time value fetched is 7:00 PM, it should display override as “FAILED”)
Is this possible?

So the time value is a string data type? 7:30 PM

yes it is