381304 PHPProBid auction script mod

I am about to purchase the PHP Pro Bid auction script (see full demo at [login to view URL]) and need to modify how seller's auction listing fees are paid. Currently, seller can either “pay as you go” or I can use accounting mode like eBay does and bill sellers. I don't want to use either; I want sellers to buy pre-paid “credits” then use them to pay listing fees. I need to have a place in admin where I can set different “packages” of credits (for example, you can buy 10 credits for $10 or 20 credits for $20 and so on - similar to the way a penny auction works.) Sellers will then have a “bank” of credits assigned to their account to pay for listing fees. The ability to add funds to a sellers account is already possible with the existing script so this shouldn't be too difficult. I also need to install the following mods to the script, and the work done must be compatible with these mods: [login to view URL] [login to view URL] Thank you for your bids, previous experience with PHPProBid is a plus, I look forward to working with you!