All of the playlists selected for updating no longer exist
One could use conditional formatting to change the background colour, but that doesn't replace an explicit message in the control.
In any case, Null is a valid value unless it's prohibited by a validation rule or automatically changed through a Visual Basic event handler, typically `after update´.
Once you know how to create a criteria where Null means “all”, you might no longer need the additional row in your combo boxes.
After opening the database in an earlier version, if the demo doesn't work, please remove any missing reference: from Visual Basic Editor, choose (Tools | References) and uncheck any libraries marked as missing.When controls on a form are used as criteria in a query, Null values usually break the mechansim.