Why can't I send a mouse click to a certain window?

So I stumbled upon dave's solution here: http://lists.apple.com/archives/Cocoa-dev/2009/Apr/msg00764.html

This basically mimics another window + sends all mouse commands over, makes complete sense. I was able to send info over to safari and navigate the web.

But when I try sending a mouse command to a game window (OpenGL powered), it doesn't do anything, at all.

Can anyone think of why this is occurring? Here is the relevant code that actuall开发者_如何学JAVAy sends the events:

ProcessSerialNumber psn;
CGEventRef CGEvent;
NSEvent *customEvent;

customEvent = [NSEvent mouseEventWithType: [event type]
                                 location: [event locationInWindow]
                            modifierFlags: [event modifierFlags] | NSCommandKeyMask
                                timestamp: [event timestamp]
                             windowNumber: WID
                                  context: nil
                              eventNumber: 0
                               clickCount: 1
                                 pressure: 0];

CGEvent = [customEvent CGEvent];

NSAssert(GetProcessForPID(PID, &psn) == noErr, @"GetProcessForPID failed!");

CGEventPostToPSN(&psn, CGEvent);

I know the app uses the following to identify events:

result = ReceiveNextEvent?(0, NULL, kEventDurationNoWait, true, &theEvent);

Thanks!