how to do in PL/SQL

hi

Error:

ORA-00984: column not allowed here

create or replace
PROCEDURE PRO_ADD_REQ_LETTER
(
 CODE in varchar2
) AS
cursor subrole is select SUBROLES from HR.ROLES where CODE=CODE';

sub varchar2(50);

val varchar2(50) :='test';
BEGIN
open subrole;
fetch subrole into sub;
close subrole;
query1 := 'insert into HR.letter('||  sub || ') values(val)';
execute immediate query1;
END PRO_ADD_REQ_LETTER;

please help

Thanks