[PayDotCom] How To Create An Payment Button With "Add advanced variables" From Paypal?

[WinsonYeung]

Hey Warriors,

I know I should have ask this question to paydotcom.com but I don't have much success in their customer support..

So I would appreciate that anyone who have any idea do help me out.

I currently have a website at http://backlinksautomation using paypal recurring payment button for the payment. I have develop my own backend system where once a transaction is received, paypal will send an notify url to my sever where my sever will create the order for the customer.

But my question is, how do I integrated that into paydotcom.com? I can't find the "Add Advanced variables" from the paydotcom.com

Example Advanced Variables.
notify_url="ht tp://example.com/paymentsuccessfully.php


How do I do that with paydotcom?

Regards,
Winson Yeung