Since there hasn't been any reply, I've managed (after many hours of work with the PHP code) to solve this.
I created a field (let's say client_id) in the form, which is made uneditable in the clients' view, and set the Client Map Filter to filter on match client_id = ID
Then, in submissions.php added a line in the create_blank_submission function that added the account_id to the client_id field when the submission was created.
Now, whenever a submission is created, the client_id is set to the account's ID number so I know who created the entry, and the filter will not allow that client to edit the field.
Of course, the field is editable by the admin and I plan to add a little sophistication in the future that will allow admin to make an individual record viewable (and so editable) to any clients by adding their ID to the client_id field (needs care in designing the logic of course).
I created a field (let's say client_id) in the form, which is made uneditable in the clients' view, and set the Client Map Filter to filter on match client_id = ID
Then, in submissions.php added a line in the create_blank_submission function that added the account_id to the client_id field when the submission was created.
Now, whenever a submission is created, the client_id is set to the account's ID number so I know who created the entry, and the filter will not allow that client to edit the field.
Of course, the field is editable by the admin and I plan to add a little sophistication in the future that will allow admin to make an individual record viewable (and so editable) to any clients by adding their ID to the client_id field (needs care in designing the logic of course).