I believe that you can only add user fields. Course id is not a user field.
When you have your Excel file, you can add this course id to the first record, then highlight down to the last record, hit ctrl-d to duplicate down.
When working with moving data to a database, it is not odd to have to do some pre-processing of the original data.
If you were good with SQL, you might be able to write a query against the database.