I have seen many related questions but didn\'t find any answer.
I have successfully implemented transactions through paypal but now I am asked to implement recurring pay
from what i understand from your question, i think paypal's Preapproval API definitely will be able to help you. I am currently working on this recurring payment as well and i manage to meet up with a paypal staff to discuss about their formula and this is what they have recommended.
You can read more about their API from my link below to understand how pre-approval works and how it can help you automatically deduct money from client's paypal account as long as they do not enter their paypal account to manually cancel the option after they opt for it.
https://www.x.com/docs/DOC-1419