You use the command in the moment you want to get the sheet.
- (void)beginSheet:(NSWindow *)sheet
modalForWindow:(NSWindow *)docWindow
modalDelegate:(id)modalDelegate
didEndSelector:(SEL)didEndSelector
contextInfo:(void *)contextInfo
sheet can be a window you created in Interface...
You're indeed missing something :-)
This allows you to have multiple Dock configurations and to switch between them. One for work, one for gaming, one for home. Nice idea. I chek if it works later.
However, it's not the solution to the question of this thread.
You have to invoke it programaticly. Currently Sheets are Cocoa-only. You can do it by [NSApp runModal:sheetname forWindow:windowname ...] or something like that. look at apple's Documentation on NSApplication. Hope this helps you.