title: How to allow to only install specific components in InnoSetup?
body: <p>So the question is this:
  I asked a question back here: <a href="https://stackoverflow.com/questions/10070493/only-allow-to-install-to-a-specific-folder-in-innosetup">How to allow installation only to a specific folder?</a></p>
  
  <p>How can I modify it a bit, so for example, I have 3 files to install, 2 of them are optional and should only be available to install, if a certain file/folder exists. I want to grey out the option to select them in the list, if the conditions are not met?</p>
  
  <p>Thank you in advance.
  Zsolt</p>