Generating an incremental number upon submission

Hi folks,

I’m working on a simple membership subscription form that collects basic user’s data at first page and then, when clicking on “subscribe” button has to generate, and display at a new page, an incremental membership number with some main data collected at previous page, like first and last name – and at the same time sends the same to the user’s email.

Example:
Page 1 will have the usual contact form fields with a subscription button
Page 2 will display the name of the subscriber, plus a generated unique incremental membership number

This second page doesn’t have any input fields, it’s only a sort of confirmation page that simply adds a unique calculated field.

Confirmation email will hold all inputs by subscriber, plus his membership number (generated by the form).

Would it be correct making the submission button conditional that reacts “when clicked” and generates a calculated field with incremental values at a new page (and sends the confirmation email), or is there a simpler solution?

Thanks!