Excel 2008 : Calculate Networkdays & 2 set of business hours

Hi, all sifu,
i have been googling a while and find no near remedy.Hope someone can help.

The current formula work very well for working business hour. Help need is: I like to include a difference set of business hours for Weekend ie: Sat and Sun.

=(NETWORKDAYS(A2,B2)-1)*(I$3-I$2)+IF(NETWORKDAYS(B2,B2),MEDIAN(MOD(B2,1),I$3,I$2),I$3)-MEDIAN(NETWORKDAYS(A2,A2)*MOD(A2,1),I$3,I$2)

A2 = date/time received
B2 = date/time answered
I3 = end of business hour (7:00am)
I2 = start of business hour (10:00pm)
J2:J4 = Holidays (If require) just add to Networkdays(x,x,j2:j4)

K2 = Start business hour 9:00 am (Sat and Sun)
K3 = End business hour 9:00 pm (Sat to Sun)

is it possible? any help appreciate. Thanks.