You could use this modification ... the two false settings will not show anything and if later you want to turn it back on, you can either put back the original code or just change them to true ...
Code:
function credit_selection() {
global $db, $currencies;
$gv_query = $db->Execute("select coupon_id from " . TABLE_COUPONS . " where coupon_type = 'G' and coupon_active='Y'");
// checks to see if any GVs are in the system and active or if the current customer has any GV balance
if ($gv_query->RecordCount() > 0 || $this->use_credit_amount()) {
$selection = array('id' => $this->code,
'module' => $this->title,
'redeem_instructions' => MODULE_ORDER_TOTAL_GV_REDEEM_INSTRUCTIONS,
'checkbox' => $this->use_credit_amount(),
'fields' => array(array('title' => (false ? MODULE_ORDER_TOTAL_GV_TEXT_ENTER_CODE : ''),
'field' => (false ? zen_draw_input_field('gv_redeem_code', '', 'id="disc-'.$this->code.'" onkeyup="submitFunction(0,0)"') : ''),
'tag' => 'disc-'.$this->code
)));
}
return $selection;
}