Multiple buttons in UINavigationItem

UINavigationItemPlus.h

@interface UINavigationItem (Extensions)

- (void) setRightBarButtonItemsWithTotalWidth: (NSUInteger) width
    items: (UIBarItem*) firstItem, ...;

@end

UINavigationItemPlus.m

static const NSUInteger kToolbarHeight = 45;

@interface SilentToolbar : UIToolbar {}
@end

@implementation SilentToolbar

- (id) initWithFrame: (CGRect) frame
{
    [super initWithFrame:frame];
    [self setBarStyle:UIBarStyleBlackOpaque];
    [self setBackgroundColor:[UIColor clearColor]];
    return self;
}

- (void) drawRect: (CGRect) rect {}

@end

@implementation UINavigationItem (Extensions)

- (void) setRightBarButtonItemsWithTotalWidth: (NSUInteger) width
    items: (UIBarItem*) firstItem, ...
{
    // Parse arguments.
    va_list args;
    va_start(args, firstItem);
    NSMutableArray *items = [NSMutableArray array];
    UIBarItem *item = firstItem;
    while (item != nil) {
        [items addObject:item];
        item = va_arg(args, UIBarItem*);
    }
    va_end(args);

    // Create toolbar with the items and insert it
    // as a custom view in place of the right navigation button.
    UIToolbar *toolbar = [[SilentToolbar alloc] initWithFrame:
        CGRectMake(0, 0, width, kToolbarHeight)];
    [toolbar setItems:items animated:NO];
    UIBarButtonItem *wrapper = [[UIBarButtonItem alloc]
        initWithCustomView:toolbar];
    [self setRightBarButtonItem:wrapper animated:NO];
    [wrapper release];
    [toolbar release];
}

@end

How can the width of the items be determined at runtime?
Whenever I try to access the item.width property, it always comes back as 0.
Any pointers appreciated,
Thank you
Nicolas Ameghino

It’s been quite long since I wrote the code, but if I remember correctly, I had to compute the width beforehand. I found no workaround.

Thanks for the answer.
I'm working around it by taking the size of the text in the button and trying to guess the button padding and spacing, but still can't get to optimal results.