Add new Filter to "Spent Time" to show users with no time-entries or below a defined time-sum

I didn't found a possibilty to show me just the users that haven't entered any times in a defined period, e.g. in "spent time" overview. We want to find out what employee has tracked less than x time in a defined period of time. So best there is a filter in the "Spent Time" overview where we can define this.

Alerts-Plugin can send emails, but an additional Overview in ER would be great.