title: How can I set the wizard to go back if an error is found in a Custom Action
body: <p>If I find an issue from within my Custom Action checks (user chose a bad install directory in the WixUI_InstallDir dialog), after I let the user know of it (by using the _session.Message), can i somehow go back to that page in the wizard (the one that shows the install dir dialog)? </p>
  
  <p>Right now I just return a ActionResult.Failure which is not ideal since he'll need to run the MSI all over again.</p>
  
  <p>Update: I just noticed that when I return ActionResult.Failure, i'm still in the wizard with the "... wizard ended prematurely" message. The Finish button is enabled but the Back is not. Can I somehow change that so that the Back is also enabled? That would solve my problem.</p>
  
  <p>Thanks.</p>