PayPal Express Custom Data Field

I have a text field where the value is being calculated and I would like to pass that value onto PayPal through the Custom Data Field.  However, the Custom Data Field drop down doesn't show the field that I need.  It shows 5 other text fields as options, but not the calculated text field.  Any ideas how I can correct this?

If you are trying to pass the calculated total value to the PayPal Express integration as the actual total cost, then that is possible by following this guide: https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field. 

However, if you actually want to pass a value in our "Custom Data Field" option in the payment integration, then you need to use a simple "Text Box" field / "Short Text Entry" field". This is why you are seeing student name fields, teacher grants and student scholarships fields are because they are also simple text boxes. You can try setting up a new text box field and use Conditional Logic to insert the calculated value there. To learn more about conditional logic, you can check this guide: https://www.jotform.com/help/57-Smart-Forms-Using-Conditional-Logic. 

I hope that helps.