Date query based on business hours

I need to create an Access query that pulls data based on an open_date and closed_date. I compute the time it takes to close a ticket on these two fields with the datediff command. The problem is the users do not work 24/7 and the time that the users are not working should not be considered. I need to calculate the hours it takes to close a ticket but not consider non-working hours. Any ideas?

Thanks!