Oracle Database Discussions

I created users in the database. I have the ability to lock some of them by calling a stored procedure from my web app :

create or replace procedure deactivate_user(login varchar2)
is
begin
    execute immediate 'alter user ' || login || ' account lock';
end;
/

Now in my web app i want to know if a particular user exists and is not locked. I tried this query to find users :

create or replace procedure user_exist(login varchar2 , ret out number)
is
    v_login utilisateur.user_login%type;
begin
    v_login := lower(login);
    execute immediate 'select count(username) from all_users where lower(username) = :1' into ret using v_login;
end;
/

So how to know that a user is not locked ?