SharePoint 2010 Calendar calculated column to exclude weekends and HOLIDAYS

I'm trying to create a calculated column to count number of days that exclude weekends and holidays

i do have the formula to exclude weekends but stuck on holidays

=DATEDIF([Start Time],[End Time],"D")-FLOOR((DATEDIF([Start Time],[End Time],"D")+WEEKDAY([Start Time]))/7,1)*2-IF(WEEKDAY([End Time])=7,0,1)+IF(WEEKDAY([Start Time])=7,2,1)

if i manually put in the holidays in the calendar (or create a list of dates) how do i get the formula to exclude those days?