The trigger below will check to see that user George is only changing his own password and not trying to change other peoples passwords.

create procedure
reset_password (p_username in varchar2,
		p_password in varchar2)
as
begin

	if (USER='GEORGE' and p_username in ('MARY','BILL','SUE'))
	then
		execute immediate
		'alter user ' || p_username ||
		' identified by ' || p_password;
	else

		send_email_to_admin
		('George is trying to amend ' || p_username || ' password');
		raise_application_error
		(-20001, 'George, you cannot change other peoples passwords');
	end if;
end;
/
grant execute on reset_password to george;