Two invoices under same agreement

 Hi
How can we take a single transaction and have it billed in two different invoices using same agreement.

We enter multiple transactions in AP all those transactions contain same agreement,but we want to invoice them separately.When we run the draft invoice process all transactions get selected but would like the ability to invoice them separately.We looked at the line grouping rules but oracle recommends not to modify them.

Any suggestions appreciated.

Thanks
Vj