Custom Segue Portrait Mode

Custom Segue Portrait Mode

I am trying to create a custom segue to change and lock my next view into
portrait mode, no matter how the device is rotated. I was able to create
my UIStoryBoardSegue files, but now I am stuck with the code to switch
from landscape to portrait... this is what I did so far:
-(void) perform
{
self.appDelegate = [[UIApplication sharedApplication] delegate];
UIViewController *source = (UIViewController *)
self.sourceViewController;
UIViewController *destination = (UIViewController *)
self.destinationViewController;
}
And now I am stuck... help!