Recurring roosters

I would love to have, recurring roosters.
As many IT specialists we have customers with contracts that wil be billed 2 hours a month.

This can be done with recurring invoicing bud then there's no way to see how many hours a specfic person (user) has made these hours.

For instance

Customer A gets billed 2 hours a month, these hours have to be on the user Dirk because he has to maintane this cutomer.