I have tried to calculate the schedule variance % with the planned start date, Planned end date,Actual start date and Actual end date in Excel. I have tried below method
=NETWORKDAYS(Planned End Date, Planned Start Date)
=IF(Actual End Date="",0,IF(Actual End Date = Planned End Date,0,IF(Actual End DatePlanned End Date,NETWORKDAYS(Actual End Date,Planned End Date)-1,NETWORKDAYS (Actual End Dat,Planned End Date))))