installments for items sent to collection agency

My client wants to create installment plans for items that have been sent to collection agency due to a unique business requirement. ISU doesnt allow installments on these items. Can someone kindly suggest a way out.

We are only using the collection agency process to track recovery of receivables which were sent to collection agency. So all we need is a report at day end mentioning the amounts that have been sent to collection agency and the payments received against those items

Any help/suggestion/hint would be highly appreciated

Regards,

Adil Kapadia