How to perform action when clicking button of NSAlertSHEET

Question

How can I perform an action when people click on "Update"?
NSAlert *alertSheet = [NSAlert alertWithMessageText:@"New update available"defaultButton:@"Update"alternateButton:@"Remenind me later" otherButton:nil informativeTextWithFormat:@"There is a new update available."];
    [alertSheet beginSheetModalForWindow:self.window modalDelegate:nil didEndSelector:nil contextInfo:nil];
I tried this:
(but this doesn't work)
NSAlert *alertSheet = [NSAlert alertWithMessageText:@"New update available"defaultButton:@"Update"alternateButton:@"Remenind me later" otherButton:nil informativeTextWithFormat:@"There is a new update available."];
    [alertSheet beginSheetModalForWindow:self.window modalDelegate:nil didEndSelector:nil contextInfo:nil];
if ([alertSheet runModal] == NSAlertFirstButtonReturn){

Answer 1

Your first step is wrong.
yourInternalFrame.addInternalFrameListener(
     new InternalFrameAdapter(){
  public void internalFrameClosing(InternalFrameEvent e){
    // do part
});