I'm developing a payment plugin for SwipeHQ (a New Zealand based online credit card processor) for my clients Drupal website running CiviCRM.

Currently a user will make a purchase and be redirected to the correct payment provider page, but is currently (incorrectly) being redirected to the IPN notification page on completion. The IPN end point should be used by the payment provider to notify the server of success or otherwise, but when the client is redirected here none of this information yet exists so it throws an exception. How do I instead redirect to the completion page ("hi your purchase is successful pending payment") - I have tried passing the URL in the format

civicrm/event/register?_qf_Confirm_display=true&e436769547477d10db6253a97538b92a_7705
But it complains about not being able to find the id..

I guess what I'm asking is, is there an easy way, given a transaction id or something similar (which I can hake the payment provider pass back to me) I can close the users current transaction?