I am working for a nonprofit managing several incoming grants from foreign donors. All donors have different requirements on what currency rates to use when creating financial reports for grants: some require the use of the curreny rate which was used when transfering the grant from the donor to us, some require a daily conversion rate from European Central Bank, some require a monhly rate set by the European Commission, etc.

Is it possible to have multiple currency rates for the same currency for the same date, and then pick which rate to use when doing (analytic) accounting? Is there an addon module to achieve this? If not, how would you suggest these feature to be programmed in a new module?