Problems with Pie Register and PayPal

I’ve installed Pie Register on my site and am trying to set up a certain workflow.

I wish to do the following:

1) The user goes to the site and sees a PayPal button. They click on it and get to PayPal, make their Payment, and get redirected to the site. This is working without an issue. I put the PayPal button as a widget on the sidebar.

2) At this point I have a registration form that requires a verification code. The form is on the screen, the verification code field is on the form and is required. The problem is that I don’t know how to automate getting that code to the user.

The ideal solution to me would be to customize the notification email that comes out from PayPal and includes a verification code (using the same one for every user is not an issue). But PayPal won’t allow us to modify the email test.

There are user notifications in PieRegister but they only fire off when the user fills out the registration form. I’d like the email to reach them BEFORE they fill out the registration form.

Perhaps I’m missing something. Does anyone know how to accomplish the following?

1) User clicks on PayPal button and makes his payment, gets redirected to the Pie Register registration form.

2) They are somehow instructed to include the given verification code. It could be on the registration form itself (in the field) but not visible before they made the PayPal payment.

3) They submit the form and are added as members to the site and get an email welcoming them.

I have worked on this for several days now and don’t know what to do.

https://wordpress.org/plugins/pie-register/