Changing file types in NSOpenPanel while it's open

I'm wondering if it is possible to change the file types in an NSOpenPanel while the panel is open...
There is an undocumented (private) instance method in NSSavePanel named _setEnabledFileTypes.
As its name suggests, its allows changing of the file type's list you pass to
Here an sample code: we have an accessory view with a matrix of radio buttons (here only two) of which action method is set to
doSelectFileTypes. The tag of the selected button cell specifies which file type's array to use:
@implementation MyWindowController

- (IBAction)doSelectFileTypes:(id)sender
curTag = [[sender selectedCell] tag] ;

[openPanel _setEnabledFileTypes:(curTag)? ([NSArray arrayWithObjects:@"xls",nil]):([NSArray arrayWithObjects:@"doc",nil])] ;

- (IBAction)doOpenAFile:(id)sender;
openPanel = [NSOpenPanel openPanel] ;

[openPanel setAccessoryView:ibAcccessoryView] ;
[ibFileTypes selectCellWithTag:0] ;
curTag = 0 ;
[openPanel setCanChooseDirectories:NO] ;
[openPanel setAllowsMultipleSelection:NO];
[openPanel setCanChooseFiles:YES] ;

[openPanel runModalForTypes:[NSArray arrayWithObjects:@"doc",nil]] ;
Of course, as usual when using undocumented feature, you should test if the method is implemented before using it for future (and/or past) compatibility.
This code has been tested under Panther only.