Variable monthly subscription cost based on usage without the need for the customer to reapprove

[raheelkhan00k]

I'm having trouble finding the correct PayPal API functions for my use case techleader. I'm looking for a variable monthly subscription. So every month we update the subscription usage. Let's say a user starts with 1 GB storage, next month the user is using 2 GB storage.

We want to bill the amount the user is using every month without going through the checkout flow again.

Anyone knows how this can be done?