Automatic Receipts in an amount different than invoice

Summary

To find out if there is a way to generate an ACH payment for amount different than invoice

Content

Hello:  We are implementing the automatic receipts method to generate ACH payments for Receivable Invoices.  A question has come up if there is a way to generate an automatic (ACH) receipt for a different amount than the invoice.  We have customers we bill damage claims, and they rarely pay what is billed, but would like to have the amount they are going to pay ACH'd.  Thanks for any information.