Is it possible to edit submitted form to add additional PayPal charge?

We're trying to build a form for a convention that has registration for the convention, plus more events. We would like to keep this simple and have only one submission per person. Is there a way to set up the form, using the PayPal payment option, that if they decide to add additional tickets to an event they can, but will only be charged for the new tickets? We don't want the people being charged twice for a registration fee.

______________________________________

Example:

Person 1 registers for the convention and one dinner event. Total = $30 + 10 = $40

        They pay $40 through PayPal.

Person 1 then decides they want their children at the dinner, so they need to add two tickets. New unpaid total = $20.

         Total for convention is $60, but they already paid $40. PayPal only charges them $20 for added tickets.

______________________________________

Is this possible???

Unfortunately, it is not possible to pay again once user has submitted the form, if they try to edit the submission they will get the payment section blocked. 

The only way to allow them to pay again would be submitting the form again, but selecting only the additional items.

You could generate a code to track or related two submissions, this is how it will work: 

1. Users will submit the form for the first time and will get a code generated.

2. You could ask on the same form if the user already purchased items previously, if they answer yes, then you could ask for the code that was generated on the previous submission, this way you know they already paid the initial amount and the second submission is a complement. 

This widget will help you generating the codes: https://widgets.jotform.com/widget/random_value_generator 

This guide will help you adding it to your form: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-your-Form 

And this guide will help you showing/hiding fields based on user's answers: https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer 

If you have any question, let us know.