How to disable Sublist fields in client script validate field

let sublistObj = currentRecord.getSublist({ sublistId: 'recmachcustrecord_jj_ia_request' });
                let objColumn = sublistObj.getColumn({
                    fieldId: 'custrecord_jj_ia_req_est_unit_cost'
                });
              objColumn.isDisabled = true;