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was used as a calculation value in a hidden field on an Interview Template in Vet, in order to create a lovely clean submission condition:
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Note that submission conditions hold for administrative users as well as applicants; in order to allow admin users to register someone via a form submission when the submission conditions are not met, just add an or statement to the filter that allows for the particular user to submit the form. (Corner case: Patty registered applicants for interviews directly in the scheduler; in order to register people for the event, we have to submit the form, which is looking for a new event registration, and cannot see the old one.)