Lockbox-Program RFEBBU00 clearing logic

Hi All,

We are calling RFEBBU00 program to post bank statements.In our requirement if 4 invoices are there for 1 remittance amount ,we want if customer is paying one check than payment should match against all instead of first one only. For this we need the logic used in program RFEBBU00 to match payments.I tried to find but could find any specific logic.Kindly provide your views.

Thanks in advance