Forms :: Allowing Data Entry For Unbound Fields (not In Table)

I'm trying to build a form based on a table where the user can also enter data to update the table but with data fields not originally in the table. Below is a summary of what I have and what I need:

1.) A file that will be uploaded daily into a Table (ie name Denials extract table).
2.) A form bound to table Denials extract
3.) Additional fields that will be updated by users that is not included in this table b/c they are not available in the system we are getting the data extract from.
4.) The user will look up a key field that will allow them to review it in our system. Once they "work" the record, there will be multiple fields that they will update with this information that are not in the bound recordsource (table Denials extract).

Do I create another table with these fields even though they will be blank at first and make them a subform that will have a "primary key field" that will link the main form with the subform? Will they need to "update" a whole new table? Not really sure how that would work since they will be updating fields not in the bound table.