How to make non-fixed-amount recurring payments?

[porton]

We want to make non-fixed-amount recurring payments to our software.

The user either enters the maximum amount he wants to pay or no maximum whatsoever so that the payment amount each month is determined by sole discretion of our software.

Please remind where such features are described in PayPal Developer docs.

[sharpiemarker]

https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/auto_bill_step_...

[porton]

But we want to do it entirely programmatically.

The link you suggested us describes at the next step to login into our PayPal account and initiate monthly transaction manually.

We want the monthly payments to be initiated by our software. How to do this?

[sharpiemarker]

Post your question about which API to use for automatic billing here:

https://stackoverflow.com/questions/tagged/paypal?sort=frequent