this is what I want to accomplish on fxts-signals:
the first time a customer subscribes, they will choose a minimum of two currency pairs @ $50 each = $100 (the minimum can be one if that is easier) – the website database does the calculation, that amount is then reflected in the payment section of the website along with the currency pairs selected, then they are directed to Paypal to complete the transaction, i.e., subscribe and pay – this will be a recurring subscription, billing each month on the same day as the customer first subscribed with all this information in the customer's admin panel. However, if at any time during the month, the customer wishes to change the currency pairs, they can do so from their customer account admin panel without any additional charges as long as the number remains two –
if they add one or more currency pairs, then the website database does the calculation (pro-rating the $50 per month charge per currency pair from the date the customer wants the additional pairs to the recurring subscription payment date), reflects that amount in their admin panel subscription section, then they go to the payment page showing that amount and are directed to Paypal to pay that amount. The problem is I can't find any documentation on the Paypal developer side to resolve this issue of adding that additional amount to the original subscription amount and having that be the recurring billing amount in Paypal. If a customer has more than two currency pairs and wishes to delete to reach the minimum number, there is no refund amount, only changing the recurring billing amount to reflect the new recurring billing amount in Paypal.
You must have extensive Paypal API developer experience.