You can open a second UIPopoverController in the same way as you called the first popoverController. But this time you nee little changes like..

You need a reference to the content view controller, you create a new UIPopoverController using

 [[UIPopoverController alloc] initWithContentViewController:content];

you set whatever properties you want and then you present it.

To present it from a UIButton or other control that isn't a UIBarButtonItem use

[popoverController presentPopoverFromRect:[control bounds] inView:control permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];

myViewController *photoViewC = [[myViewController alloc] initWithNibName:@"myViewController" bundle:[NSBundle mainBundle]]; 

UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:photoViewC]; 

popover.delegate = self;
[photoViewC release];
self.popoverController = popover;
[popover release];

popover.popoverContentSize = CGSizeMake(450, 680);
[popover presentPopoverFromRect:CGRectMake(260, 0, 120, 120)
inView:self.view permittedArrowDirections:UIPopoverArrowDirectionLeft animated:YES];