Homemade nori -> aonori?
The nori that you buy as sheets is usually a different species than that of the form prepared as aonori. The form that you buy in sheets is, additionally, typically roasted, which changes the flavor.

Aonori is usually of the genus Monostroma or Enteromorpha. Toasted nori for sushi is usually of the genus Porphyra.

Because of those two details, I don't believe you can get the same results from grinding up nori. However, that's not to say that it can't be done if the taste satisfies you. I sometimes grind nori furikake (which contains small strips of nori) not to simulate aonori, but just to get the nori and sesame to adhere to other ingredients (like popcorn).