The answer here, pulled from the comments, was to drop the existing table and replace it with one that is more properly normalized. The structure of the new table will be something akin to the following:

Likely foreign keys: ItemGroup, CountryCode Likely unique index: ItemGroup + CountryCode

This table structure allows a selection by either ItemGroup or by Country to get the desired Rate or rates. A join to a country detail table can provide the additional information if required and a join to an Item table can provide information about the item.