What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I am afraid you can not do that on JotForm's Form Builder directly as it is preprogrammed into Jotform.
However, you could do that outside of JotForm by downloading the Form's source code and host the files in your website. You can then hook in using your scripts.
Depending on your goal, you can also use our Conditions feature to instruct the form on some other things that it will must do after clicking the Submit button. Please see this overview guide Smart Forms Using Conditional Logic
If you need further assistance, please do not hesitate to ask for help. Thank you