You can open a child subview that obscures the parent (i.e. it is the same width and height, has a grey background, and consumes touches), and then open a subview in that subview that handles your user interaction.
You can make your obscuring view transparent if you want to show the actual parent superview, you just have to make sure in the first-layer subview you catch all touches and don't allow them to be passed to the parent superview. See this post for info: how to prevent a touch event passed to a UIView's superview?