Unfortunately this is not possible with the current paypal relationship we have.
Their current APIs/SDKs do not support this functionality. They used to, but now it's closed (adaptive payments). We are working on getting special approval to use the feature, but otherwise we cannot do this :(
Same with Sezzle for example - these types of redirect payment-methods means that we cannot charge a user without their expressed consent at the time of purchase
We are working to make progress with PayPal, and if we do, I will open this back up!