Vendor Exchange Rates - AX 2009

When I apply an exchange rate to a vendor that differs from the main exchange rate that is set up in the GL, this is not pulled through when processing an invoice - it pulls through the system exchange rate.

This is also thecase if you adjust the exchange rate on an invoice when matching to a PO - this adjusted exchange rate is ignored and it reverts bck to the system exchange rate.

Does anyone have a solution for this please?