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How to change a text box to only allow usernames that haven't been submitted previouslyAsked by jonathanpiechnik on January 06, 2015 at 06:07 PM
Hi, Is there any way to allow for clients to fill in a username that they'd like while also keeping them from using usernames that others have used previously?
Are you perhaps referring to unique question submission.
Check this user guide -How-to-set-Form-Limits-Based-on-a-Unique-Question
When you assign a field as a unique question, it will prevent submissions if the same answer is provided to that unique question on the form. This will then prevent duplicated answer on that particular question.
Hope this help. Let us know if you need further assistance.