How to pass the amount to PayPal from another form field?

At CLC Ottawa we calculate our user's tuition cost using a variety of logic, then when the user selects PayPal payment the dollar amount is taken from a form field containing the calculated total. The URL below is for a typical form that uses this method. 

I am now trying as a volunteer to help another charity, Kanata United Church, to improve its summer camp registration form. When I try to set up similar logic, the PayPal integration does let me specify User Defined Amount, but it does not let me choose a field from which to take that value. The only option is is manually entered value. 

Is using a field not available to organizations at Bronze level? They are actually paying more than CLC Ottawa pays during the months when we drop back to a free plan because we get almost no registrations. 

Here is the URL of a my partially built new registration form for their camp:

https://form.jotform.com/91710616121244

https://form.jotform.com/91710616121244

https://form.jotform.com/91710616121244https://form.jotform.com/91710616121244

https://form.jotform.com/91710616121244

Sorry about the multiple URLs. When I pasted, it did not appear in the editor. 

Please note that you can only pass the value to payment field using Form Calculation widget. Please use Calculation widget for the field which you wish to pass instead of using normal Number field.

Let us know if you still face the issue.