title: Is there any way to wait for a PostMessage to be processed by the recipient?
body: <p>I encounter the problem, that after posting some WM_KEYDOWN/WM_KEYUP messages, I need to use Thread.Sleep for like at least 200ms, before then to post WM_LMOUSEDOWN/WM_LMOUSEUP messages. If I don't do this, the recipient processes the mouse click first, which means the earlier keystrokes go to the wrong position of the target handle.
  I cannot use SendMessage, because the recipient ignores those as WM_KEYDOWN/WM_KEYUP.</p>
  
  <p>Is there any way to wait for a PostMessage to be processed?</p>