Below solution works for me.
(Switch(Mod(StartDate.SelectedDate - Date (1985,6,24),7),
0, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,2,2,3,3,4,4,5,5,5,6,5,1),
1, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,2,2,3,3,4,4,4,5,4,6,5,1),
2, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,2,2,3,3,3,4,3,5,4,6,5,1),
3, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,2,2,2,3,2,4,3,5,4,6,5,1),
4, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,1,2,1,3,2,4,3,5,4,6,5,1),
5, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,0,2,1,3,2,4,3,5,4,6,5,0),
6, Switch( Mod( EndDate.SelectedDate-StartDate.SelectedDate,7),1,1,2,2,3,3,4,4,5,5,6,5,0),
999)
+ RoundDown(((EndDate.SelectedDate-StartDate.SelectedDate)/7),0)*5
- Sum(Filter('Public Holidays', Date >= StartDate.SelectedDate And Date <= EndDate.SelectedDate),No_x0020_of_x0020_holiday))/If(HalfDay.Value = true,2,1)