Custom Price Based on Metals Spot Price + Markup - Magento Extension

I require a Magento extension that works similar to [login to view URL] I do not require a purity option but do need to be able to specify which metal, IE: gold, silver, platinum or palladium. I need the options to be configurable in the price options in the admin portion of Magento. For each metal • Set weight (oz or gram). • Set Markup eg. 10% or $10. - Uses our real time gold price feed to list precious metals items on the Magento eCommerce CMS. - Calculations must be: Product Price = precious metals price + markup - Prices need to be updated continuously, but once a product is placed in the cart it should hold the same pricing for several minutes, long enough to complete the transaction. - I need to be able to add weight and markup amount or percentage. If you have any questions please ask before bidding. I am only looking for developers that have completed this type of work before, working examples will need to be supplied. If you haven't completed this work before, please do not apply. Please note, this project is for setting up the online price calculations and integrating the feed.