How do I pass hidden fields to PayPal

On my form https://www.jotform.us/form/62437775023154?preview=true, I would like to pass the "Submission Number" and "Mother-Son 2016" fields to PayPal so I can reconcile.  How do I do that?  

Thanks!

It is possible to pass custom fields to Paypal. That is found under "Additional Gateway Settings".

Here's how:

As you could see, you can only pass one field to Paypal.

However, there's a trick on how to pass the 2 fields value by combining their values into a single textbox field and use that field on Paypal.

Okay, let says you have 3 fields. 1 & 2 fields that you want to combine and 3 as the output field. To do that, simply create an Update/Calculate Condition.

Here's an example condition:

Then use that output field on Paypal

Hope this helps!