Customer Information, credit accounts, paying down account.

First, some of you old hats may have seen my name around a year ago. Unfortunately because I moved to a new state I had to close my store (more complicated and irrelevant). Throwing around the idea of using ZenCart to expand a friends tool "truck" to a web based system. As it is now he has his customers and we all have an "in house" tool credit.

Is there an add-on or module to add the ability for a customer to have a credit or account. Example, I want to give some customers $1000 in credit, I also want the customer to be able to see there credit limit and Balance when they are logged in. Also is there a way that I can give the customer a button to pay off some of their bill (or all of it for that matter)?

Please bare with me here peeps, I'm just getting back into it and back into my very very amateur web programming.

Thanks

You could use the Gift Certificate to give customers 'credit'. They could use this as the payment method for orders. Their 'balance' would be the remaining gift certificate value. Not exactly what you're asking, but maybe of some help.