Contractor hours paid/unpaid

It would be nice if somehow we have the option to keep track of which hours made by contractors have been paid to them already. This should be seperate from the invoicing to clients.

As an example our current situation:

1 contractor working on 2 projects at once. They both have been invoiced to the client. One invoice by the contractor has been received. The contractor will have extra work on the project next week.

You can see how it would help if I could be sure everything was administered in Harvest :)