Date and Time Difference with two Date range

=DaysBetween([Creation];[ModifiedDate]) * 86400

+

(

ToNumber(FormatDate([ModifiedDate] ;"hh")) * 3600 +

ToNumber(Left(FormatDate([ModifiedDate] ;"mm:ss") ;2)) * 60 +

ToNumber(FormatDate([ModifiedDate] ;"ss"))

)

-

(

ToNumber(FormatDate([Creation] ;"hh")) * 3600 +

ToNumber(Left(FormatDate([Creation];"mm:ss") ;2)) * 60 +

ToNumber(FormatDate([Creation] ;"ss")))

I want to calculate Weekends with this Formula.

Thanks

ram