Well I'm not in SP 2007, but I would ask you some questions, to get a better idea of your aim.
What do you mean with "automatic upload"? Is there a central storage to upload from or is there a local storage for every user?
Is there be a upload-directory where the documents are placed to be uploaded? Well in SP 2010 you can do the automatic upload with SharePoint Workspace, an additional tool from Microsoft.
If you want to implement a upload-routine on your own, you could implement a tool with C# that pushes the documents in a library.
You could also use the SharePoint Webservices.