Virtuemart Discount Plugin

Hello, I need a plugin for Virtuemart v2.X under Joomla! 2.5.x This plugin need to do the following: Allow to add discount base on total amount to be purchase: if a client spend from.. let say: 10usd to 100usd they will get a 3% discount if they spend from 200 to 500usd they get 10% discount and so on... I prefer to enter the % or fixed amount in the backend, but it can be done hard code, it doesn't manner... It doesn't manner if they buy a single article, the total to be paid for that article is $20usd then they get a 3% discount... if they buy 20 items and the total amount is 201usd they get a 10% discount... Please let me know time and rate Thank you.