IPN paypal and others

[seb14]

Hello,

Sorry for my approximativ english (i'm french).

I installed joomla virtuemart 2 to 2.5 and I try to change the paypal ipn file (or any means of payment way).
Indeed, I have a site with restricted to subscribers (paid) section and I hope that when the customer has paid it is assigned directly to a joomla "subscribers" group and the expiry date of the contract be update in my mysql table dedicated.
I have the mysql tables. Until this transaction was perfectly through paypal buttons and ipn script I had changed, but then I do not see ipn script in ftp.
How to retrieve variables (I made a basket with variations depending on the length of subscription) and call in the ipn file?
I found this file: httpdocs / plugins / vmpayment / paypal / paypal / helpers / paypal.php
is it good? how to call the variables change?
thank you for your help.