Change allowed file types based on certain criteria An admin comes onto the website and creates an assignment which is a content type.  Students come onto the website and create submissions that point to the certain assignment.  There is a file upload field where students can upload their submission.  I want to make it so when the admin creates the assignment, he/she can choose which file types are allowed.  Is there a field that will automatically process what file types the admin chose so that a student can only upload that specific file type?
So, it's the rough instruction step by step as Matt asked:


Add new field where you can specify the allowed extensions of the files.
Alter the form of your submission via hook_form_alter() and find your file upload field 
Specify your allowed extensions from your field with extensions into this point