AutoCalendar NFC Logging Time Duration into Google Calendar

Need help,trying to log my hours for certain task via NFC task to google calendar.I have managed to link NFC tag via tasker to log in the timei do a certain task,but iam unable to log the "duration" of that particaular task on google calendar.
Is there a certain add-on that i can use or is there a certain function within Tasker that i can use to monitor the amount of hours?