creating calculating column to know the days remaining before due date?

I want to create a calculated column which shows the remaining days before due date. that calculated column should exclude weekends, has to count only business days. I found one article, this is what i want exactly but it seems not recalculating for next day. Let's say for one item we have 7 days more to the due date for today and it should be 6 days more for tomorrow. the article is: http://www.sharepointoscar.com/blog/2008/06/24/sharepoint-list-calculated-column-calculate-business-days/

Please help me.

Ramanjulu Naidu N