Keep a reference to a file after it has moved in objective-c?

I have a Cocoa application that stores a reference to multimedia files (images, videos, etc) on the user's computer. I'm wondering if there is a way to get a reference to that file other that using a file path so that if the user moves that file to a different folder on their computer, I would still know where it is. I'm currently storing the array of file paths that are passed back from the standard Cocoa open dialogue:

-(void)addMultimediaDidEnd:(NSOpenPanel*)sheet
           returnCode:(int)returnCode
          contextInfo:(NSString *)contextInfo 
{   
    if(returnCode == NSOKButton) {
        [sheet orderOut:nil];
        [self saveFiles:[sheet filenames]];
    }
}