Automated random work schedule

Thank you very much.

The only thing that's missing me know is the randomized process. When i update excel then there should be new employees every time still trying to come close to there number of hours they should work.
I think at work, variety is always good.
How can I randomize that and automate it so I don't have to put the employees in manually?
Furthermore, I would need the possibility to indicate when a person can not work and this date/dates are then automatically not entered for this employee.