Hi @aaronrobb
I’m afraid you can’t do it. ACF has a hook to modify the taxonomy query, but it can only access the data saved in the database, not the one changed on the editor page. This page should give you more idea about it: http://www.advancedcustomfields.com/resources/acffieldstaxonomyquery/.
Could you please tell me what you want to do with the parent taxonomy? I believe a term object has a “parent” attribute which you can get easily.
I hope this helps.
