Forward exchange contracts are used to hedge purchase orders and sales orders in foreign currency.
The exchange rate for these FX contracts should be able to be applied against purchase order/customer lines when posting those transactions.
A FX contract should show what PO/SO transaction line has consumed the FX amount available, and what the running balance of the FX contract is available.
The FX contract should be able to settled when making payment to a vendor
The Fx contract should be able to be roll over and costs calculated.