We would like a way to remove the weekend hours from the the clock used to track ticket: hours since created/updated ( or open, pending...)

We are a school district and want to give our agents 3 business days to update/solve a problem.  Currently we can do hours since update is equal to 72 but if a ticket is created on a Thursday or Friday, then we would want to give them 120 hours so the weekend does not count against them.

Thank you