How can you discard the current event from the event queue

I want to trigger mouse right click actions whenever the user hits the mouse button while pressing the control key.

This has until now been accomplished by replacing a mouse click event with the control key modifier with a mouse right click event inside a specialisation of the NSApplication method nextEventMatchingMask:untilDate:inMode:dequeue::

Code Block 
//When current event matches mouse click with ctrl key pressed create mouse right click event
event = [NSEvent mouseEventWithType:NSEventTypeRightMouseDown 
...]
//Discard current event and replace it with the new event
[_currentEvent release];
_currentEvent = event;
[event retain];

This works, but manipulating _currentEvent directly is no longer allowed. I then tried to use the following to discard the current event and replace it:

Code Block                
[self postEvent:event atStart:YES];
[self discardEventsMatchingMask:mask beforeEvent:event];

Although the new event does get inserted into the queue, the original event is still there.

So can you tell med what I am missing? Or should this not be handled in the NSApplication subclass at all? Thank you very much in advance!