I tried the provided sheet but I think the formula needs to be amended to fulfill my criteria because I need the formula to exclude the following from the final result:

1) All Fridays and Saturdays hours
2) Non-working hours from Sundays, Mondays, Tuesdays, Wednesdays and Thursdays

Expected Result from the given dates

Start Date and Time 07/09/2013 9:30:00 AM = Excluded
08/09/2013 = 9 Hours
09/09/2013 = 9 Hours
10/09/2013 = 9 Hours
11/09/2013 = 9 Hours
12/09/2013 = 9 Hours
End Date and Time 13/09/2013 4:00:00 PM = Excluded

Final Result = 45 Hours
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Another Example

Start Date and Time 18/09/2013 7:00:00 AM = 9 Hours << as anything before 8AM should be excluded
19/09/2013 = 9 Hours
20/09/2013 = Excluded
21/09/2013 = Excluded
End Date and Time 22/09/2013 7:00:00 PM = 9 Hours << as anything after 5PM should be excluded

Final Result = 27 Hours