Handling Chargebacks

Good Morning SAP Guru's-

I need a solution for my customer. In payment processing, the majority of work is a result of deductions or chargebacks. The customer is taking a deduction against an invoice or against a reference number the customer provided. I understand the residual process or leaving a balance on account and adding a reason code if you want. I was wondering if there is another option. This option, I know can work by inputting the chargeback number in the assignment field however it will leave the document with the check number in the reference field. My customer wants a way to create a new document with the chargeback number in the reference field much like creating a debit memo. The trick here is they want it done during postprocessing(FLB1, FB01, FB05). Can this be done? Any other ideas?

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