The following code shows you how to use OnChange to submit your form if the value of your "title" field is "Other":
if (document.details.title.value == "Other")
<form name='details' method='post' action='formhandler.cgi'>
<!-- rest of your form -->
When you receive this at the server, you then need to test for title=Other, and if so send a new form back to the client with your "title" field now being a text box. Leave it with the name "title", and you can just use the same code to commit the form to your database when the form is submitted for the second time.
Don't forget to pre-populate the new form with any fields that had already been completed - or you'll have some very unhappy nearly potential customers!
Hope this helps!