Im looking for assistance with this module...

I need to change a payment module redirection when it errors.

Currently its refering to checkout_payment but obvously this page is no longer used when in 1 page checkout.

Here is the code:
PHP Code:
zen_redirect(zen_href_link(FILENAME_CHECKOUT_PAYMENT, 'error_message=' . urlencode(MODULE_PAYMENT_STGEORGEHPP_TEXT_FAILED_MESSAGE . " " . $response_text), 'SSL', true, false)); 
How can i change this code to refer back to this page correctly so i dont get a 406 error?
PHP Code:
index.php?main_page=checkout&action=null 
I need it to redirect back to this page so payment can be re done.