title: Sending WM_COMMAND to a TMenuItem
body: <p>In my Delphi form's OnShow method, I determine that a dialog must be opened automatically once the form is opened - and I should be able to do this by simulating a click on a menuitem.</p>
  
  <p>However, calling menuitem.Click brings up the dialog before the main form has opened - which is not what I want.</p>
  
  <p>I expect that should do what I want, but I cannot find what parameters to pass for "wparam" to send the click to my menuitem. </p>
  
  <pre><code>PostMessage(handle, WM_COMMAND, wparam, 0)
  </code></pre>
  
  <p>The <a href="http://msdn.microsoft.com/en-us/library/ms647591%28VS.85%29.aspx" rel="nofollow noreferrer">MSDN WM_COMMAND docs</a> talk about IDM_* identifiers, but how does that appear in Delphi?</p>