Wix Forms Transaction Field

Question:
Hi, I’m currently working on a website for a summer day camp. I was working on a registration form for it where you can fill out your camper’s info and then pay by the camper. The way it works is let’s say you have 3 campers, you click the drop down menu and click 3, using a rule in the form feature, it will reveal 3 registration boxes for the campers. The only issue is that there is that for some reason you cannot add a “Transaction Field” to a rule, it just simpily doesn’t show up. I was wondering if anyone knew how to fix this or if there is any work around? (I will link some picutres as well)

Product:
Wix Studio Forms Feature

What are you trying to achieve:
I want it so that I can hide the transaction box and it will be revealed only upon the selection of a drop down box from a previous question.

What have you already tried:

Additional information: