Passing calculations to Payment Field

I'm trying to use your directions, but when I select User Defined Amount I can only find "None Manual" in the "Get Price From" drop down box.  I'm using the Matr Boomie/For Kids form.

I see that your form is already configured with some products so that the total amount will be calculated automatically. If you want to display the total on the form, you may enable the option from Gateway additional settings.

If you want to use the custom calculation on your form and pass it to the payment field, it is required to be a calculation field to pass the value to the payment field. Please refer to the guide below that can help you with this.

https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

Hope this information helps! 

I think the problem may be that I’m using the purchase order form. When I select the user defined amount it does not give me the “calculate” option – only the “none (manual)”
Daniela Vognar
Daniela Vognar
Owner | Noah's Gifts and Gallery | P.O. Box 171, Wabasha, MN 55981 | Phone: 608-237-1410 | http://www.noahsgiftsandgallery.com | Email: daniela@noahsgiftsandgallery.com
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When it says None, that means you do not have a calculation widget in the form. You need to have a calculation widget in the form to get the total. You should see this calculation in the dropdown.

https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form