Magento create csv address details and add to invoice email

Magento 1.6.1 we have fooman email attachements insalled and also their pdf customizer. What we need is to automatically create a special csv/txt file that contains label information for GLS shipping company. (can be provided) This file needs to be attached to the transactional invoice email only. Currently fooman attached the incoice as pdf and also add a txt file with terms and conditions. This needs to works only for 3 specific shop in our magento multistore. The cvs file would be imported by our supplier in their gls label lite software enabeling them to automatically print a shipping label. I would like this as an extension and no core changes.