master detail open programatically ios

This is doing my head in... (iPhone only, it works on iPad) Take the template "master detail", in the detail view you see the left UINavigationBarItem which triggers the step back to the master.

When you replace that NavigationBarItem, it loses the target and action, fair enough.

How to trigger this manually, i've tried all ... [navBarButtonOpenMenu addTarget:self.splitViewController action:@selector(_triggerDisplayModeAction:) forControlEvents:UIControlEventTouchUpInside]; does nothing

fetching the target and selector from the current UINavBar left button doesn't work (reference will be lost i would imaging)...

I would just like to manually trigger open and close with custom button (close bing back to current detailviewcontroller)