Is there a way to know how much time passed from when I called WaitForSingleObject function untill it returned?
or that the only way of knowing is by using some kind of a timer?
Just store current time before calling WaitForSingleObject(). Then compare to time when it returns.
From http://msdn.microsoft.com/en-us/library/windows/desktop/ms725473(v=vs.85).aspx - select a function to retrieve time.