Unfortunately, the working day calculations in QV have a fixed weekend of Saturday and Sunday, so you will have to roll your own.
What I would do is include a working day as a field in your calendar, having a value of zero for Fridays and Saturdays and 1 for working days. You could then sum working days to get a NetWorkDay equivalent that you could then plug into the suggestions in the link above.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein