Hi JayL,
There is a technical article on CustomerSource that describes how to do this. Search for Article ID 844270. Here is a sample from the article (Only one currency can be used per batch, but the rate and rate type may change per line):
Currency, CAD
CuryRate, SPOT, 03/03/2003, .74
"Batch",,200501,"H",100.00,
"Document",,"VO","VENDID",03/03/2003,,03/03/2003,01,100.00,0,"A",,,,,03/03/2003,,,,,,,,,,,,,,,,,,,,,,,,
"Transaction","N",5200,,,0000,,,,,100.00,,,,,,,,,,,,,,,,,,,,,
You may be able to access the article directly through this link.