Redirect on node form submit with custom module - hook_form_alter

Question

I have Druapl 6 with orgranic groups installed. I need a thing - when a group user creates "group" content after node form submission he must be redirected back on group homepage instead of node view page.

function heihachi_form_alter(&$form, $form_state, $form_id) {
  switch($form_id) {
        case 'group_wall_node_form':
        unset($form['buttons']['preview']);

        $redirect = 'node/' . $form['og_initial_groups']['#value'][0];
        $form_state['redirect'][0] = $redirect;
        //dpm($form);
        break;
  }
}

but that code doesn't redirect at all. Using simple $form['#redirect'] works, but it affects Node delete button aswell, so i can't delete my node because it redirects on a custom path. Thanks for all advices in advance.

My new code (not working also):

function heihachi_form_alter(&$form, $form_state, $form_id) {
  switch($form_id) {
        case 'group_wall_node_form':
        unset($form['buttons']['preview']);
        $form['#submit'][] = 'custom_redirect';
        //dpm($form);
        break;
  }
}

function custom_redirect($form, &$form_state) {

  //unset($_REQUEST['destination']);
  //unset($form['#redirect']);

  $form_state['rebuild'] = TRUE;

  $redirect = 'node/' . $form['og_initial_groups']['#value'][0];
  $form_state['redirect'] = $redirect;
}

This is what i see in $form variable:

0 (String, 21 characters ) menu_node_form_submit | (Callback) menu_node_form_submit();

1 (String, 31 characters ) auto_nodetitle_node_form_submit | (Callback) auto_nodetitle_node_form_submit();

2 (String, 15 characters ) custom_redirect | (Callback) custom_redirect();

I guess something wrong is there?

SOLVED!

used hook_nodeapi as one guy told me below:

function heihachi_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
  if ($node->type == 'group_wall') {
    if ($op == 'insert') {
      $_REQUEST['destination'] = 'xxx';
    }
  }

Answer 1

use hook_nodeapi with op insert or add another submit function in hook_form_alter.