Here is the formula that I have now, that works, that is not excluding weekend days:
ToHours(If([Task Status]="Completed",[Deadline]-[Time Completed],[Deadline]-Now()))
Here is what I tried to do to modify it but it isn't working:
ToHours (If([Task Status]="Completed",WeekdaySub ([Deadline],[Time Completed]),WeekdaySub ([Deadline],Now())))