actually, the files I'm working on are already in XML and I'm using an XML editor to fill it. But I'd like to continue working on it with a form, rather than writing directly in the XML editor.
The problem is, who (or more specifically, what code) is going to read your form and write the XML?
If it's not a web page, then you'll need some custom user-interface code to present the form to you.
Some other piece of code has to take your input and generate the XML.
Then it has to be saved to the disk somewhere.