A way to do the same using Excel worksheet functions only:
1. Add a helper column into your table, where all table rows are numbered <e.g. =(ROW()-HeaderRowNo)>;
2. Add a helper column into your table, where all table rows for every supplier are ranked by rate date <using COUNTIFS like =COUNTIFS(SupplierRange, SupplierInRow, RateDate, "<=" & DateInRow)>;
To get the latest rate for any supplier on any date, you have to combine INDEX and SUMIFS functions to return the rank from proper row. The formula will be too complex for me to write it down on fly!