I want to collect and validate a value (PIN) in a Google Form. The Form has 2 pages, and I\'d like the validation to affect form navigation:
Not sure you can do this with Google Forms and Apps Script.
But I have done exactly this with UiApp/Html Service in Apps Script. I used it for a light-duty user authentication.
You are not able to create this type of dynamic form using the Google Forms Service, because there is no interaction between the service and scripts during form entry, except upon Form Submission. In the case of a multi-page form, a script has no way to know that a user has completed one page and gone on to another.
You could achieve this using the HtmlService or UiService, by writing your own form.