The link that follows should take you to a spreadsheet that you can view that has been created for a couple of purposes.
These Orders list every regiment that was part of the Army of Northern Virginia that was involved in the Maryland Campaign. The listing then has companies A - K (except J) listed. In each cell where you see an "X" it indicates that the webpages on this site have been read and checked against the official rosters of the campaign.
I have notated in the original spreadsheet who created what company and the date of formation, so if there are more than one group claiming a company name, you members can PM me and I will let you know who to contact so you can work out arrangements.
There is also, if you scroll down far enough, links where these rosters were found and below that, a revision and revision date as more companies are formed and added to the charts. I will be updating as I see the changes. Also below these links, starts a second chart which lists all the companies that are formed for the Confederate forces that are not officially associated with the Orders of Battle for Antietam. This doesn't make you wrong.