search for email that I have not responded to   

I am using Microsoft Outlook 2003
I want to search my outlook email on periodic basis for email that I have 
not responded to. Every day, I get hundreds of emails. I always wonder if I 
responded to all the emails. 


Is there a way to use Advanced Search feature to find the email I have not 
responded to quickly?

date: Fri, 7 Sep 2007 16:34:01 -0700   author:   Subbu