Add a file upload to spreadsheet app

Question

Created a wizard-generated out of the box app based on spreadsheet.
Now I want the ability to store a file attachment for each row. So I added the file_id column to the table as a FK to my custom table which stores the uploaded files.
What is a good UI to handle updates to this?
On the Create page, I added a File Browse box to upload the file, works fine.
Added a Download link on the report page, also works fine.
On the Update page, how should this file_id field be handled? There need to be 2 options (that I can see)
a. delete the file (delete it from the custom table and null out the file_id column)
b. replace it with a new file (delete the old file from the custom table, upload the new file and update the file_id pointer)
How can this be done on the wizard-generated Update Form page?
Thanks

Answer 1

OK this is what I ended up doing
On the Update form, I added a Display as Text item and created an OnLoad computation to populate it with a Download link
select '< a href="foo.download_file?p_file_id='||file_id||
       '">< img src="/i/themes/theme_10/showhide_show.gif" / >< /a >'
from mytab
where id=:P3_IDAdded a File Browse item (P3_FILENAME).
Added a After Submit process that fires after the wizard-generated Automatic DML process that does
DECLARE
  l_file_id  NUMBER;
BEGIN
  IF (:P3_FILENAME IS NULL ) THEN
    RETURN;
  END IF;
  DELETE FROM myfiles
  WHERE       file_id = (SELECT file_id
                         FROM   mytab
                         WHERE  id = :p3_id);
  UPDATE mytab
  SET    file_id = NULL
  WHERE  id = :p3_id;
  INSERT INTO myfiles (file_id,file_name,mime_type,file_size,created_by,created_at,blob_content )
  SELECT id,
         filename,
         mime_type,
         doc_size,
         updated_by,
         updated_on,
         blob_content
  FROM   htmldb_application_files
  WHERE  NAME = :p3_filename;
  UPDATE mytab
  SET    file_id = (SELECT id
                    FROM   htmldb_application_files
                    WHERE  NAME = :p3_filename)
  WHERE  id = :p3_id;
  DELETE FROM htmldb_application_files
  WHERE       NAME = :p3_filename;
END;In plain English:
1. Allow the user to view/download the file
2. If they select/enter a file in the File Browse box, delete the existing file and replace it with the new file and store a pointer to it in the table.
It is working like a charm.
Hope this helps someone.