Hey there @imJihyo! Maybe you can use a calculated field to check if the code is valid OR existing inside your code table, then use JavaScript to prevent the submission?  I created one DataPage for creating payment confirmation codes. This one makes you enter the name of the customer then it generates a random ID as the code: Then, for the form that the users will fill out, I used a combination of calculations and JavaScript.  Here's the calculation (you can use a virtua