Short answer is: yes, you can.
Unfortunately, to explain it in further detail, I would need to try the procedure myself, but I'm not submitting an article right now, I don't remember what happens on each step. Besides, the procedure could have been modified since my last submission (it looks like it is generally improved). But I remember that you can submit the article in all steps, close the session and revisit your article when you log again. The article is not actually submitted as a final version and its URL does not appear on the news and search until you explicitly confirm it is final. After that step, the article becomes available to the readers as unedited. I've been able to fix the article after that, until it is edited by an editor member.
When the article is accepted for editing, you will be given a direct contact with the editor, so you will be able to coordinate your further steps with the editor and ask your further question. The editors are very collaborative and helpful. When the status of the article changed to edited, you can only send your updates through the editors.
I just checked it up: you need to load your article and click "Update your article" and you will see what to do next. In earlier stage you would be able to update the article exactly in the same way as during submission, but when the article is edited, you will need to post/send your message and the file with changed to the editorial board.
I would advise you to go ahead and submit the article even if it needs updates. In case you have problems, you will be given a contact to the editor who could help, in worst case.
If you are still in doubt or have a problem, you probably can ask a question here: http://www.codeproject.com/Forums/1645/Site-Bugs-Suggestions.aspx
]. Even though this is a zone for bugs and suggestions, the post there are scanned by people developing the site on a regular basis. I always got some reply in a reasonably short period of time.