function add_new_article_simple_page() {
  module_load_include('inc', 'node', 'node.pages');
  $node_form = new stdClass;
  $node_form->type = 'announcement';
  $node_form->language = LANGUAGE_NONE;
  $form = drupal_get_form('announcement_node_form', $node_form);
  return $form;
}

function add_new_article_form_alter(&$form, &$form_state, $form_id){
  if($form_id=='announcement_node_form')
  {
    $form['#after_build'][] = 'add_new_article_after_build';
    $form['account_password'] = array(
        '#title' => 'Parola',
        '#type' => 'password',
        '#required' => TRUE,
    );
    $form['#submit'][] = 'add_new_article_form_submit';

    return $form;
  }
}

function add_new_article_form_submit($form, &$form_state){
  $email=$form_state['values']['field_email']['und'][0]['value'];
  $password=$form_state['values']['account_password'];
  //check if the email even exists
  if(!db_query("SELECT COUNT(*) FROM {users} WHERE name = '".$email."';")->fetchField())
  //create the new account
  {
    $edit = array(
        'name' => $email,
        'pass' => $password,
        'mail' => $email,
        'init' => $email,
        'roles' => array('4' => 'standard user'),
        'status' => 0,
        'access' => REQUEST_TIME,
    );
    $loc_var=user_save(drupal_anonymous_user(), $edit);
    $GLOBALS['new_user']=$loc_var->uid;
  }
  else
  {
    //check if username + password are valid combination
    if($uid = user_authenticate($email,$password))
        //log in user after account creation
    else
        //this is where I want to interrupt the submission of the form
        form_set_error('account_password', 'Parola nu este buna pentru acest email.');
  }
}

function add_new_article_form_validate($form, &$form_state)
{
    $email=$form_state['values']['field_email']['und'][0]['value'];
    $password=$form_state['values']['account_password'];
    form_set_error('account_password',t('The form is being validated.'.$email.' and '.$password));
}