iOS How do I gray out UIWeb Back Button and Forward Buttons?

#import <UIKit/UIKit.h>
@interface Web: UIViewController {
	UIWebView *webView;
	UIActivityIndicatorView *activityIndicator;
	NSTimer *timer;
}


@property (nonatomic, retain) IBOutlet UIWebView *webView;
@property (nonatomic, retain) IBOutlet UIActivityIndicatorView *activityIndicator;
@property (nonatomic, retain) NSTimer *timer;
@end

#import "Web.h"


@implementation Web

@synthesize webView;
@synthesize activityIndicator;
@synthesize timer;

- (BOOL)shouldAutorotateToInterfaceOrientation:
(UIInterfaceOrientation)interfaceOrientation {
	return (interfaceOrientation !=
			UIInterfaceOrientationPortraitUpsideDown);
}

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
	[webView addSubview: activityIndicator];
	self.title = @"MacRumors";
	
	NSString *urlAddress = @"https://www.macrumors.com/";
	NSURL *url = [NSURL URLWithString:urlAddress];
	NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
	[webView loadRequest:requestObj];
	timer = [NSTimer scheduledTimerWithTimeInterval:(1.0/2.0) target:self selector:@selector(loading) userInfo:nil repeats:YES];
	
	
	
	
}
-(void)loading{
	if(!webView.loading)
		[activityIndicator stopAnimating];
	
	else
		[activityIndicator startAnimating];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning]; // Releases the view if it doesn't have a superview
    // Release anything that's not essential, such as cached data
}


- (void)dealloc {
	
	[webView release];
	[activityIndicator release];
	[timer release];
    [super dealloc];
}


@end

#import <UIKit/UIKit.h>
        @interface Web : UIViewController {

	UIWebView *webView;
	UIButton *back;
	UIButton *forward;
	UIActivityIndicatorView *activityIndicator;
}

@property(nonatomic,retain)IBOutlet UIWebView *webView;
@property(nonatomic,retain)IBOutlet UIButton *back;
@property(nonatomic,retain)IBOutlet UIButton *forward;
@property(nonatomic,retain)IBOutlet UIActivityIndicatorView *activityIndicator;

-(IBAction)backButtonPressed: (id)sender;
-(IBAction)forwardButtonPressed: (id)sender;
@end

#import "Web.h"
@implementation Web
@synthesize webView;
@synthesize back;
@synthesize forward;
@synthesize activityIndicator;


//method for going backwards in the webpage history
-(IBAction)backButtonPressed:(id)sender{

	[webView goBack]; 
}

//method for going forward in the webpage history
-(IBAction)forwardButtonPressed:(id)sender{

	[webView goForward];
}

//programmer defined method to load the webpage
-(void)startWebViewLoad{

	
	NSString *urlAddress = @"https://www.macrumors.com/";
	//Create a URL object.
	NSURL *url = [NSURL URLWithString:urlAddress];
	
	//URL Requst Object
	NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
	
	//Load the request in the UIWebView.
	[webView loadRequest:requestObj];
	
}

// acivityIndicator is set up here
- (void)viewDidLoad {
	
	//start an animator symbol for the webpage loading to follow
	UIActivityIndicatorView *progressWheel = [[UIActivityIndicatorView alloc]
                            initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

	//makes activity indicator disappear when it is stopped
	progressWheel.hidesWhenStopped = YES;
	
  //used to locate position of activity indicator
	progressWheel.center = CGPointMake(160, 160);

	self.activityIndicator = progressWheel;
	[self.view addSubview: self.activityIndicator];
	[self.activityIndicator startAnimating];

	[progressWheel release];
	[super viewDidLoad];
	
	//call another method to do the webpage loading
	[self performSelector:@selector(startWebViewLoad) withObject:nil afterDelay:0];  
	
}


- (void)dealloc {
	[webView release];
	[back release];
	[forward release];
	[activityIndicator release];
    [super dealloc];
}

#pragma mark UIWebViewDelegate methods
//only used here to enable or disable the back and forward buttons
- (void)webViewDidStartLoad:(UIWebView *)thisWebView
{
	back.enabled = NO;
	forward.enabled = NO;
}

- (void)webViewDidFinishLoad:(UIWebView *)thisWebView
{

	//stop the activity indicator when done loading
	[self.activityIndicator stopAnimating]; 

  //canGoBack and canGoForward are properties which indicate if there is 
  //any forward or backward history
	if(thisWebView.canGoBack == YES)
	{
		back.enabled = YES;
		back.highlighted = YES;
	}
	if(thisWebView.canGoForward == YES)
	{
		forward.enabled = YES;
		forward.highlighted = YES;
	}
	
}

@end