Hi Arthur,
Welcome to the board! I don't quite understand your first paragraph. If you put your forms in a SharePoint form library, you can use a SharePoint views to filter and sort the forms for opening. You can also use a SharePoint list adapter from within InfoPath to list them, but I think the SharePoint views are better here. If you need to create custom code from your form that enumerates the items from a folder on your local computer, you will have to write custom code. Ideally, you'll want to put your forms in a database and have some query and filter logic in your form to help you find the right one.
Hope this helps, but I'm a little unsure it will.
Patrick Halstead [InfoPath MVP]
InfoPathDev
Patrick Halstead
Project Manager at Qdabra