Hi Kay,
Does your current credit card processor offer an electronic method to submit credit cards for authorization? If so, can you get the file layouts required from them? You might find that you can create the necessary upload file using GridView or another reporting tool.
We have implemented Pre-authorized Debit (PAD) processing for a few clients using Adagio Invoices who wished to directly debit their customer's bank accounts for payment (rent). I would expect that credit card processing would be similar, and we would be willing to look at this as a custom project for you.
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Andrew Bates