Its there a way to put a margin top to a rightBarButtonItem ?

Question

I'm trying to possition a rightBarButtonItem in my toolbar, is there a way to do this? Im using a pretty standard navigationBar, this is the code:

[[self.navigationController navigationBar] setTintColor:[UIColor blackColor]];
self.navigationItem.rightBarButtonItem =
[[[UIBarButtonItem alloc] initWithTitle:TTLocalizedString(@"Cerrar", @"")
                                  style:UIBarButtonItemStyleBordered
                                 target:self
                                 action:@selector(cerrar:)] autorelease];

I have tried this but didnt worked:

float topInset = 4.0f;
self.navigationItem.rightBarButtonItem.imageInsets = UIEdgeInsetsMake(topInset, 0.0f, -topInset, 0.0f);

Thanks!