@protocol changePictureProtocol <NSObject>
-(void)loadNewScreen:(UIViewController)*controller;
@end

@property (nonatomic, retain) id<changePictureProtocol> delegate;

-(IBAction)changePicture:(id)sender
{
    // ..... blah blah
    [self.delegate loadNewScreen:picker];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
   // create cell here

   cell.delegate = self;
}

-(void)loadNewScreen:(UIViewController)*controller;
{
  [self presentViewController:controller animated:YES completion:nil];
}

CustomCell *customCell=[tableView dequeueReusableCellWithIdentifier:@"CellIdentifier"];
[customCell.yourButton addTarget:self action:@selector(yourButtonAction:) forControlEvents:UIControlEventTouchUpInside];