Google Shopping feed required for Joomla Virtuemart CMS website.

After a recent upgrade of the website the existing Google Shopping feed does not work. The Google Crawler picks up the current text fie every day from as specified location - that bit works fine. However, the file contain invalid links to images and products. Basically the PHP script that creates this file is part of a scheduled task on the server and it needs looking at so that the links it provides are valid along with any other links to images etc. The solution will either be from a new plugin or from altering the current PHP file so that the correct fields are used and created. The final solution has to be automatic with no manual input and ideally there will be some control over where the PHP script or plugin takes information from which products. Ideally the solution will allow me to point to a special category so that only product I target will be part of the final feed for the Google Shopping Feed. As Google Shopping uses specific type images with regard dimensions and sizes it will be necessary for the solution to be able to target specific images relating to each product. These might not necessarily be the primary image for that product on the website as the primary image may not always be ideal for the likes of Google Shopping thumbnails. Please note that any automated application will not be considered and your application will include the words "Google Shopping !$&"