Computing Business Hours

I am attempting to compute Service Levels for an interaction based upon business hours. For example, an email arrives at 4pm and is handled the following day at 10am. Call Center Hours are 8-5.

Essentially I have a number of different alternatives, and have found some potential solutions, including:

www.dbforums.com/arch/7/2003/9/914261

However, my situation has a couple of additional twists to the standard 8hrs of business M-F. The call center is open different hours depending upon the day of the week. For example, 8-5 M, 10-7 T, 8-5 W Th F, 10-2 Sat, 10-12 Sun

Additionally, I would like to remove Holiday's from the calculation for service level as well.

I have explored a number of different table DTD's, but none seem to be a perfect fit for determining the number of "open" hours between when an interaction arrived, and when it was handled.

The DTD I have for the Holiday table is as follows:

CREATE Table Holidays (HolidayDate DateTime)
GO
Insert Into Holidays (HolidayDate) Values ('12-25-2004')


Please let me know what you feel would be the DTD for storing the business hours and also the query for extracting the number of Open hours between two dates

Thank you in advance