add shipping options to WP Marketpress site

hi there I have a WP site that's running Marketpress. I also have a list of freight options to different places around Australia. So I these freight options need to be added to Marketpress so the shopper can select their nearest freight depot and Marketpress will automatically add the correct price to the checkout. This needs to be done in a way that wont be overwritten during a Marketpress upgrade. So either as a separate plugin or as a Marketpress Addon. You will need to install the plugin / addon to the actual site and ensure it doesn't break the theme or any other plugins that are currently installed. To be eligible for this project please quote "Pinky"