title: Attach an OnChange handler to existing textbox control NSIS
body: <p>I'm trying to attach an onchange event handler to the existing Install directory textbox in NSIS. However, it never seems to trigger. Any ideas how I can do this? </p>
  
  <pre><code>GetDlgItem $TextControl $HWNDPARENT 1019
  GetFunctionAddress $R0 MYFUNCTION
  nsDialogs::OnChange  $TextControl $R0
  </code></pre>
  
  <p>I've used Resource hacker to get the control ID and I added the above code to a MUI_PAGE_CUSTOMFUNCTION_SHOW before displaying the MUI_PAGE_DIRECTORY.</p>
  
  <p>Any help on getting a function to trigger on an already existing control would be greatly appreciated. </p>
  
  <p>Thanks</p>