calculating number of days without weekend and holidays

Hallo all,

can someone help me with a formular to calculate the number of days with Crystal Reports 2008 between two dates without weekends and holidays

eg.

date one = 03/24/2010

date two = 03/29/2010

Result should be 4 days as 03/27 and 03/28 will be a weekend.

Plus how to exclude holidays ?

Thank you very much

Gerald