For the example in the photo:
If the Status is 'In Progress' the Actual Start Date will have the today's date or when you click the 'In Progress', then when you click the 'Pending' the Actual Start Date's value should remain to when the date you click it. May I know what condition I can use?
=IF(Status@row = "In Progress", "", IF(Status@row = "Pending", TODAY())