tracking NSTextField changes

I am working on a project to add metadata to mp4's. I am tracking which fields have been altered, but the code looks "clunky" and not elegant to me. I hope someone can help me streamline this a bit.
Thank you alot,
                          Todd

- (void)controlTextDidChange:(NSNotification *)aNotification
{
    if ([aNotification object] == directorField) [textChanges setObject:@"changed" forKey:@"directorChanges"];
    if ([aNotification object] == writerField) [textChanges setObject:@"changed" forKey:@"writerChanges"];
    if ([aNotification object] == castField) [textChanges setObject:@"changed" forKey:@"castChanges"];
    if ([aNotification object] == producerField) [textChanges setObject:@"changed" forKey:@"producerChanges"];
    if ([aNotification object] == typeField) [textChanges setObject:@"changed" forKey:@"typeChanges"];
    if ([aNotification object] == showNameField) [textChanges setObject:@"changed" forKey:@"showNameChanges"];
    if ([aNotification object] == episodeNameField) [textChanges setObject:@"changed" forKey:@"episodeNameChanges"];
    if ([aNotification object] == airDateField) [textChanges setObject:@"changed" forKey:@"airDateChanges"];
    if ([aNotification object] == episodeNumField) [textChanges setObject:@"changed" forKey:@"episodeNumChanges"];
    if ([aNotification object] == seasonNumField) [textChanges setObject:@"changed" forKey:@"seasonNumChanges"];
    if ([aNotification object] == theCompanyField) [textChanges setObject:@"changed" forKey:@"companyChanges"];
    if ([aNotification object] == theRatingField) [textChanges setObject:@"changed" forKey:@"ratingChanges"];
    if ([aNotification object] == albumField) [textChanges setObject:@"changed" forKey:@"albumChanges"];
    if ([aNotification object] == thePlotField) [textChanges setObject:@"changed" forKey:@"plotChanges"];
    if ([aNotification object] == ProductionCodeField) [textChanges setObject:@"changed" forKey:@"productionCodeChanges"];
}