Creating Days Past Due Calculated Column (using Monday-Friday work week)

Hi everyone,

I created a calculated column that displays the number of days (past due or until due) an item is based on a 'Date Due' date column:

=[Date Due]-TODAY()

If the item is 'past due', the number is displayed as a negative.  If the number is 'until due', it is displayed as a positive.  This is perfect, but I'm wondering if there is a way to customize the formula to only take into account the Monday-Friday work week.  For example, if the 'Date Due' field shows Monday, November 1st and the current date is Monday, November 8th, the 'Days Past Due' calculated field would display a -5 instead of a -7.

Many thanks!