Config Zen to accept cust-specified payment

[envisionit]

I am looking to use Zencart to accept invoice/bill payments from customers. Basically I am looking to have a system that the customer enters their customer information (name, address, phone number, etc...), enters an invoice number, enters how much they want to pay on the invoice, and enters the credit card info. Can I configure ZenCart to allow processing an amount that is specified by the customer? I already have a gateway and a merchant account setup but I do not know how to go about accepting a payment specified by the customer. I would also like to constrain the minimum and maximum just to make sure I dont get any one cent payments or any million dollar payments, but I can do the coding for this myself if needed.

Thanks for any suggestions,

Bob

[Merlinpa1969]

create a $1 called pay your invoice,
make it non taxed and free shipping,

modify the test to say enter payment amount here,

whole dollars ONLY