GREP Style that creates fractions but makes exceptions for 9/11

I had this working great until someone asked a great question.

"It works.  It changes 5/6 and even 67/128 to fractions, and it respects dates like 12/25/13.  But when it comes to 9/11, can you make an exception in the GREP?"

Here is my GREP code within the Para Style:     (?<!\d)(?<!\d/)\d+/\d+(?!/\d)(?!\d)