Right, as davidcland said - you need to talk to Apple and they will just allow you to do so. They will enable this for you and then you need to handle the technical part yourself. Apple will allow you to do this for a month or so, after that you wont be permitted. If you need in future, you need to talk to them again.
Well, now the technical part. Try this tool for help, its written on Apple Script. Remember its a third party and no one can guarantee the performance: http://www.enterpriseios.com/wiki/Batch_Apple_ID_Creator
