You need 3DS Max to edit units for RTW and you need Vercengetorix's CAS importer
http://www.twcenter.net/forums/downl...do=file&id=141
to get them to load / export.

You can use the import function of that with Gmax as well, but unfortunately the export part does not work on that program, so you'd have to find someone with 3DS Max to send your Gmax model to, to get them to convert it for you.