I am building a program, and I want to do the following: When a user presses a specific button, I want to display some names in a window containing a table view. The user must select one of these names, and he/she must press ok. Then the value selected will be returned, and I must do something with it (which is irrelevant). What I don't know is how can I lock the rest of the user interface when displaying this panel. By the time the panel is displayed, I want force the user to make a choice! I don't want the user to be able to tackle with the rest of the user interface until he makes a choice. How do I do that? Is there any way that can be done using something else (sheets?)?