Purchase in Foreign Currency with Multiple GR but single Invoice - URGENT

Question on the following scenario:

- Purchase order is foreign currency.

- Multiple goods receipts posted against the PO on different dates. Goods receipts will follow the posting date for the exchange rate.

- Single invoice receipt for the multiple goods receipts

We need the invoice to not result in exchange rate differences for all the line items. If it was just a single GR, we can change the IR header exchange rate to be equal to the GR exchange rate. The problem is for multiple GRs with multiple exchange rates.

Thanks for your help!