Hi Katie,
Thanks for posting in the community, I’m glad to offer help.
According to your description, you can try to set the “Closed Date” column as “Calculated” type instead of “Date” type, so that it can return values via a formula based on other fields, here are the steps:
Click “+Add column” > More… > choose “Calculated (calculation based on other columns)” > type the formula =IF(Status="Open",Status,IF(Status="Closed",TODAY(),"")) > set the return value type to “Date” > save the changes.
Please note that the “Calculated” column is only used to return values, it cannot be used to input data or edit the returned value.
Hope the above method can help you, please feel free to let me know if it works or you have any concerns, I’ll continue to help you.
Best Regards,
Arck