title: INNO Setup: How to implement file update based on different versions of the application
body: <p>I have an application written in Delphi that has several versions that contain binaries and database (MDB) with catalog data.</p>
  
  <p>During the product life cycle fixes/enhancements are either in database file or in some binary files.</p>
  
  <p>Version are preserved in Registry. </p>
  
  <p>Users might have different versions of the program when new patch is available.</p>
  
  <p>Now users have different versions how to implement following scenario in Inno Setup:</p>
  
  <ol>
  <li>If user have version A prevent installation. </li>
  <li>If user have version B copy db over and file1, file2, file3. </li>
  <li>If user have version C just update file1.</li>
  </ol>
  
  <p>What is the correct way to implement this in Inno setup?</p>