Dynamic Field Adition / Subtraction using FAPI
if (!isset($form_state['values']['number_subscribers'])) {
   $form_state['values']['number_subscribers'] = 0;
}

for($i = 0; $i &lt; $form_state['values']['number_subscribers']; $i++){
$form['subscribers_wrapper_container'][]['UCM_SUB'] = array(
    '#type' =&gt; 'textfield',
    '#size' =&gt; 30,
    '#title' =&gt; t('Subscriber IP Address'),
    '#required' =&gt; TRUE,
  );
}


You should add '#tree' =&gt; TRUE on your form, it will be easier to extract the form values afterwards