how do i tell CST that my costs are in different currency than ledger currency.

due to some restrictions, we want to maintain the item costs and material trx in USD, even tho our primary ledger would be in BRL. what this means is even tho our PO's wil be in BRL,, at the time of PO receipt we want to convert them into USD and store them in mtl distributions
so when the user runs the inventory reports is there any way to tell the system that the mtl distributions are in USD and we want them to convert it into BRL.
pls share your thoughts on this,
thanks,lakshmi jagarlapudi.