transaction notification

kindly find the below code that i want to prevent update on JE

Can any one help me

IF (:transaction_type = 'U' ) AND :object_type = '30' THEN

select distinct T0."TransId" , T0."Memo" FROM OJDT T0 INNER JOIN JDT1 T1 ON T1."TransId" = T0."TransId"

WHERE T0."TransId" = list_of_cols_val_tab_del;

error := -100;

error_message := N'You Cannot update remark on JE' ;

END if;