Every area has it's own MLS system so it's possible that there's an MLS # that would be used in say Chicago IL and in Chapel HIll NC. If you know a specific MLS # you're interested in you can search by the niumber this way on Realtor.com and on Trulia once you get down to the city level.
Hope this helps.
There are a few options as many of the agents have said previously. I am a REALTORÂ® in your local area and I have access to all of the MLS #'s in our area. Most info is available online as our MLS does syndicate to many sites around the web. However let me know if you haven't found the information that you needed as I may be able to help