The tricky part pertains to how you control the specific data in a revision. For example, how would the revision that changed the egg component of the recipe from "add 4 eggs" really be different from "eggs: add 4"? That problem aside, though, if all you want to do is make sure entries are unique you would use the Aggregate Record widget in the script builder side of the script editor to count the number of records in that form that already have that value in that field. Then using either or both the On Input script and/or validate script you would either set the field back to a starting value or cancel the submit if the count is more than 1.
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