title: Inno Setup - Display MessageBox to run additional file
body: <p>I am new to Inno Setup and having difficulty find this answer...</p>
  
  <p>I have included a DirectX9 setup file in the installer, but I want to display a MessageBox to the user to ask "Do you want to install DirectX9?" that is done before the regular installation of my game... if he says yes, then I want to run this additional file that I included, but otherwise just proceed to install the game.</p>