How to calculate workdays

Dear excel forum,

i have problem in calculating wordays
commonly, there are 5 workdays in a week.
What about 6 days? Because my offday just on friday.
Count
start day 01/10/2013 sunday ?
End day 31/10/2013 monday ?
Tuesday ?
Holiday 14/10/2013 wednesday ?
15/10/2013 thursday ?
Friday ?
Saturday ?

Offday=saturday,sunday
workday 21

offday=friday
workday ???
LIKE IN ATTACHMENT

Thank you!

Try the improved NETWORKDAYS function by Chip Pearson

Wow, it works Pepe...
By the way, what about the calculating the days? Such as in my attachment:
Sunday ... days?
Monday ... days?
And so on
Thank you

hi mnur. maybe this in E2:
=SUMPRODUCT(--(TEXT(ROW(INDIRECT($B$2&":"&$B$3)),"dddd")=D2))
if you exclude the holidays, it would be:
=SUMPRODUCT(--(TEXT(ROW(INDIRECT($B$2&":"&$B$3)),"dddd")=D2),--(COUNTIF($B$5:$B$6,ROW(INDIRECT($B$2&":"&$B$3)))=0))

thanks benishiryo,
i've tried the formula, it works very well.