passing form values

Hi all,

I have a form which passes some value to the submit function based on a parameter. This submit function then links the user to some page. My code looks like this.

/*
 * form to create a button which links to view page
 */
function scribblar_button_form(&$form_state, $appointment){

    $form['appointment'] = array(
        '#type' => ' hidden',
        '#value' => $appointment
    );

    $begin = db_fetch_array(db_query("SELECT begin FROM {appointment} WHERE id ='%s'", array($appointment)));
    if(strtotime($begin['begin']) <= (time()+300)){
        $form['submit'] = array(
          '#type' => 'submit',
          '#value' => t('Ga naar de les'));
    }else{
        $form['submit'] = array(
          '#type' => 'submit',
          '#disabled' => TRUE,
          '#value' => t('Ga naar de les'));
    }
    
    return $form;
} 

function scribblar_button_form_submit($form, &$form_state){
    drupal_goto('/scribblar/view/appointment/'.$form_state['values']['appointment']);
}

However, for some reason I can't seem to put my finger on, $form_state['values']['appointment'] doesn't seem to exist. I first thought it had sth to do with me referincing $form_state etc. in the wrong way. So I messed around with the function parameters a bit but this didn't solve it either. I use pretty much the same code (put param in hidden field then use in submit function) in another module and this works just fine.

Any help would be greatly appreciated. Thanks in advance,
Bouke