i am working on a project with a lot of reports, some are due on Daily, weekly, monthly, quarterly, annually basis. they are all different type of reports and assign to one group of guys.

I have started by adding three columns: 1) a yes/no column - add reminder 2) an options columns with choice: 4hrs, 1day, 2days, 1week - Reminder Time 3) a calculated column which would calculate Time&Date reminder should go out - Reminder Date

but my calculated formula below for the reminder date column is not working or allowing me to save it:

=IF([Add Reminder]="Yes",IF([Reminder time]="4hours before", [Start Time]-(4/24), IF([Reminder time]="1day before", [Start Time]-1, IF([Reminder time]="2days before", [Start Time]-2, IF([Reminder time]="1week before", [Start Time]-7))

The point of this formula is to send a reminder out base on what choice the event organizer choose from the reminder time

Any help with this formula and finishing the process would be greatly appreciated.

thanks,