I ocationally find your question because I don't subscribed the topic: one has on the stackoverflow more better notification system as here.
Abou your question I don't full understand your problem. How I can see from the fist look at the source code the documatation is correct and beforeCheckValues will be really called with 3 parameters. So if you don't receive the 3-d parameter you should post the code which you use. On the other side I don't understand why the 3-d parameter can be interesting bacause you can define separate parameters for Add and for Edit forms (see prmEdit and prmAdd parameters of navGrid).
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