All of us EDI geeks will need more information. Is the GM of which you speak General Motors; like it automobile production? They tend to have specific EDI formats for their industry. Also, Gentran comes in several flavors on multiple platforms. You will need to be a bit more specific. Also, is this for SAP as GM uses SAP in most divisions?
Be more specific and we will try to help.
Cheers,
Skip Stein