Prosites Integration with Affiliate Networks

Hi

I am using Affiliates Plugin with Prosites. I want to replace the affiliates plugin with an affiliate network managing my affiliate.

I have a question regarding integration with Affiliate Networks.

I need to put some pixel tracking code (supplied by the affiliate network) in the page that confirms the Paypal Payment (The page that handles the Paypal IPN).

I have set my Paypal IPN to post to :
http://mysite.com/wp-admin/admin-ajax.php?action=psts_pypl_ipn
(as explained in the setup)

Could you please tell my which physical php page/file handles this IPN message? I need to add the pixel tracking code into this page.

Could you also confirm that this will work?

Thanks