Preventing field modification of one field based on other fields
I have a table with a 'Status ' field with a value list of Closed , Cancelled , Ongoing.
I have 2 other fields (time fields ) 'pick up time' and 'return time'
How can I prevent the 'Staus' field being modified to 'Closed' when the 'Pick up time' and 'return time' are empty.
ie. the status field could only have the closed status when the time fields have been filled.