00 Cavalier squealing noise from front tire?

I have had a constant sqealing noise in my front tires(not sure wich side) for about a month now, I took it in to a shop today and they took a look and said that they could not find anything, "it's like looking for a niddle in a hay stack" is what the service advisor told me. any suggestions?

well its either the tabs on the front brakes telling you its time for new brakes...it could also be the front wheel bearings