Custom Mod for Zen Cart

Hi, I need a custom mod for zen cart which allows me to put a separate entry called surcharge upon checkout. This module should allow me to: 1. input a fixed or percentage surcharge 2. the surcharge should be based on payment method. 3. display the surcharge at the check out payment page 4. i should be able to sort the order of display of this surcharge myself in the future under Order Total Thank you so much Thank you