Custom form: submit function not working

Hey,

I started working on a (my first) custom form module, which purpose is to edit existing non-Drupal database tables. The current code is based on examples from the Pro Drupal Development book and this post I found on drupal.org. After 2 days of struggling to get the submit function working, I was hoping maybe one of you guys could point me in the right direction.
The contents of my .module is as follows:

// $Id$

/**
 * @file
 * Module for editing db-tables with maintenance objects.
 * Inspiration and major part of the code: http://drupal.org/node/1019526
 */

/**
 * Implementation of hook_perm().
 */
function form_ldl_perm() {
  return array('query database');
}

/**
 * Implementation of hook_menu().
 */
function form_ldl_menu() {
  $items['landgoed/landgoed-de-laan/bevraag-db'] = array(
    'title' => 'Wijzig beheerobjecten',
    'page callback' => 'form_ldl_query_db',
    'access callback' => 'user_access',
    'access arguments' => array('query database'),
    'type' => MENU_NORMAL_ITEM,
  );

  $items['landgoed/landgoed-de-laan/bevraag-db/edit/%beheerobject'] = array(
    'title' => t('Edit Form'),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('beheerobject_edit_confirm', 4),
    'access arguments' => array('query database'),
    'type' => MENU_NORMAL_ITEM,
  );  
  
  return $items;
}

/**
 * Page callback for the overview page where you can select maintenance objects.
 */
function form_ldl_query_db() {
  $header = array(t('Code'), t('Waterkeur'),  t('Lengte'), t('Breedte'));
  $query = "SELECT * FROM {ldlwlijn}";
  $rs = db_query($query);
  $row = array();
  if ($rs) {
    while ($data = db_fetch_object($rs)) {
      $code = $data->code;
      $waterkeur = $data->waterkeur;
      $lengte = $data->lengte;
      $breedte = $data->breedte;
      $row[] = array($code, $waterkeur, $lengte, $breedte, l(t('Edit'), "landgoed/landgoed-de-laan/bevraag-db/edit/$data->code"));
    }
  }
  $str .= theme_table($header, $row);
  return $str;
}

/**
 * Implementation of hook_load() (as far as I know now)
 */

function beheerobject_load($beheerobject) {
  $query = "SELECT * FROM {ldlwlijn} WHERE code = '%s'";
  $rs = db_query($query, $beheerobject);
  if ($rs) {
    while ($data = db_fetch_object($rs)) {
    return $data;
    }
  }
  return FALSE;
}

/**
 * Function called on load of the edit form page.
 */

function beheerobject_edit_confirm(&$form_state,$beheerobject){
  $form = array();
 
  $form['waterkeur']=array(
    '#title'=>t('Waterkeur'),
    '#type'=>'textfield',
    '#default_value' => $beheerobject->waterkeur 
  );
  
  $form['lengte']=array(
    '#title'=>t('Lengte'),
    '#type'=>'textfield',
    '#default_value' => $beheerobject->lengte 
  );
    
  $form['breedte']=array(
    '#title'=>t('Breedte'),
    '#type'=>'textfield',
    '#default_value' => $beheerobject->breedte
  );
  
  return confirm_form($form,t(''),
    isset($_GET['destination']) ? $_GET['destination'] : "landgoed/landgoed-de-laan/bevraag-db",
    t(''),
    t('Edit'),
    t('Cancel'));
  }

/**
 * Implementation of submit function. (function name + _submit)
 */

function beheerobject_edit_confirm_submit($form, &$form_state)
{
  if ($form_values['confirm']) {
     $waterkeur = $form_state['values']['waterkeur'];
     $lengte = $form_state['values']['lengte'];
     $breedte = $form_state['values']['breedte'];
     
     $query = "UPDATE {ldlwlijn} SET waterkeur = '$waterkeur', lengte= '$lengte', breedte = '$breedte' WHERE code='%s'";
     $rs = db_query($query, $beheerobject->code);
  }
  $form_state['redirect'] = "landgoed/landgoed-de-laan/bevraag-db";
}

I'm a newbie to custom module development, so if you need more info, please don't hesitate to ask. I would be very grateful if someone could point into the right direction!

Thank you in advance!

MF