Create UDF For Currency Conversion With VBA Only - No External Connections

The main objective is to create a, UDF with 2 parameters (Currency, Date) in order to display currency exchange rate based on the currency and date. Let's say I want to find an exchange rate between USD/ EUR, then I would have a formula something like "=FX(EUR, 12/31/2011)". All currencies will be against USD.

The trick is that it will have to be created as Add-On so that it can be used in any Excel spreadsheets. The second trick is that I cannot have VBA to make any internal connections to other workbooks or applications.

So the only thing that I can come up with would be to write a VBA code that would include all values and currency rates in it. The structure that I have in mind would be something like:

Code:
Function Fx(Vl As String, Dte As Date)
Dim Rte As String
If Vl = "EUR" And Dte = "12/31/2011" Then
Rte = 0.7723
ElseIf Vl = "EUR" And Dte = "12/31/2010" Then
Rte = 0.7546

[code]....

The above code does not work!There will be at least twenty different currencies and at least 15 periods.