Disable interaction with main window, while other window is open

Question

I have a main window where all the work is done. When i open the preference panel I would like to freeze the main windows as long as the preference panel is open. For example iTunes: as soon as i open the preferences i just can interact with preference panel and nothing else.

Is there an easy way to archive this behavior?

Answer 1

Code:

[NSApp runModalForWindow:theWindow];