Calculating days Network days and federal holidays

I need to determine if the date a form was submitted was on time (within 3 days of the request) but I do not want to penalize them for weekends and Federal holidays. I need to be able to take a date and calculate using that date plus 3 days but not including the weekends or federal holidays. So for example:

Col. A: Request Date Col. B: Due Date Col. C: Formed Rec'd Col. D: Days Late
06/30/2011 07/06/11 07/08/11 2

I need a formula to calculate Col. B (Col. A plus three days not incling weekends and federal holidays) then a formula to calculate Col. D (Col. C - Col. B)

Please help.

Try

=WORKDAY(A2,3,holidays)

where holidays is a list of those federal days.