Enabling custom fields after form datasource marked not editable

I have base code which is disabling a form datasource from edit after a status is achieved (e.g., shipped). The table has been enhanced with custom fields. What the business would like is the ability to modify our custom fields regardless of the status of the record. Part of my question is, if the form datasource is already not editable, am I able to enable our custom fields (and controls) to allow edit? Some instructional steps would be greatly appreciated. Thank you!