Validation Rule AJAX

HI
On a form we want to be able to have a field that a user is required to enter a tag number they have. We want to validate they have a valid code and also populate some other details based on data stored against their tag.
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Is there any way I can do all this via AJAX as my test did not work as validation is check before the AJAX returns and I prefer to do this via AJAX instead of submitting the form. Currently I have a variable set that that the AJAX updates to se it to be valid or not. I would like to know is there a better way of doing this?

Hi grantdigital,
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I would do this with a multi-page form and have just the tag number check on the first page, then you can use an Event Switcher on submit to check the tag and either show a message or preload and display the test of the form.
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Bob