drag for two UIScrollViews
===

I have two UIScrollViews, aScroll and bScroll. And the bScroll is the aScroll's subView. Problem I am facing is, i want to drag in bScroll and do not affect the aScroll. 
Can someone help me here??
Thanks.

    - (void)viewDidLoad
    {
    [super viewDidLoad];
    UIScrollView *aScroll = [[UIScrollView alloc] initWithFrame:CGRectMake(50, 50, 400, 400)];
    aScroll.backgroundColor = [UIColor grayColor];
    aScroll.contentSize = CGSizeMake(401, 401);
    [self.view addSubview:aScroll];
    [aScroll release];
    
    UIScrollView *bScroll = [[UIScrollView alloc] initWithFrame:CGRectMake(75, 75, 150, 150)];
    bScroll.backgroundColor = [UIColor lightGrayColor];
    bScroll.contentSize = CGSizeMake(500, 500);
    [aScroll addSubview:bScroll];
    [bScroll release];
    
    UILabel *bLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 20, 30, 30)];
    bLabel.text = @"B";
    [bScroll addSubview:bLabel];
    [bLabel release];
    
    UILabel *aLabel = [[UILabel alloc] initWithFrame:CGRectMake(100, 250, 100, 40)];
    aLabel.text = @"A";
    [aScroll addSubview:aLabel];
    [aLabel release];
    }
