Default Invoice exchange rates entered by user while doing payments

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Is any way to default Invoice exchange rates entered by user while making payments through PPR run,

Requirement - I have 50 invoices where invoice currency e.g USD and payment currency e.g RUB is different for one BU where user is entering different conversion rate for each invoices. while doing payments through PPR, system should pick all 50 invoices with user entered conversion rates mentioned in each invoices

Issue - Above process is not happening in the system, instead of that system is asking to entering one conversion rate i.e USD to RUB for all 50 invoices if we select conversion rate type as user. However we have 50 conversion rates entered by user for each invoices.