How to activate autoresponder with PayPal IPN?

Hi everyone,

I have put up a "PayPal Buy Now" Button on my site generated from the PayPal merchant tools page.

If someone makes a purchase of my product thru my "PayPal Buy Now" button I would want it activate my autoresponder to send out a Thank You message to my customer. I do understand that PayPal has a IPN but do not know how to get this to activate my autoresponder.

Would apprecaite if someone could advise me on this.

Thanks you & regards

William