XI/ABAPR/3 solution Decision

Hi

We have a process where our vendor sends a C.S.V file everymonth listing all the invoices they have sent in that month.

We are required to authorise those invoices by changing a field in the C.S.V file from "null" to "A".

I would like to know various solutions by which this process can be implemented using XI and R/3 .

One of my solution was to make R/3 make a file with the list of authorised invoice numbers each month , and XI can compare these numbers against the invoice numbers in the C.S.V file and if its true the field is changed to "A".

But the problems i see with this solution is how to send the list of files from R/3 to XI. I dont want to use BPM because of performance issues.

second problem i see is i need to store all the list of invoices in a queue at runtime to compare them against C.S.V invoice numbers.

What other solutions can be used for this process. I would liek to hear about your thoughts