Default Value for Custom Field
I did this by using CiviCRM hooks (BuildForm).

($form == CRM_Core_Action::ADD) {
        $currentDate = date('d/m/Y');
        for ($i = 1; $i &lt; 10000; $i++) {
            $defaults['custom_197_-' . $i] = $currentDate;
            $form-&gt;updateElementAttr('custom_197_-'. $i,array('readonly'));
        }
        $form-&gt;setDefaults($defaults);
       } 


This is working