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.
You will need to use conditions to achieve this, this way you will be able to display a message indicating that the entered value cannot be the same in both fields.
Here's a guide that will help you to show or hide fields based on other fields answer: How-to-Show-or-Hide-Fields-Base-on-User-s-Answer
Here's a demo form that I made: https://form.jotform.com/63184810284961
Feel free to clone it by following this guide: How-to-Clone-an-Existing-Form-from-a-URL