Hi Vamshi,
Following logic gives the number of working days excluding weekends in sql,
datediff(dd, inv.schedule_start, inv.schedule_finish) - (datediff(wk, inv.schedule_start, inv.schedule_finish) * 2) -
case when datepart(dw, inv.schedule_start) = 1 then 1 else 0 end +
case when datepart(dw, inv.schedule_finish) = 1 then 1 else 0
You can use above logic to build your expression in calculated attribute.