Shred horseradish on food processor grater. Then shred beets (directly on top horseradish). Remove food from processor. Remove grater attachment and attach blade. Dump grated horseradish and beets in and process, adding vinegar, salt and sugar mid way, to make a pasty sauce. Stop machine, taste some horseradish on a piece of matzoh. Adjust seasonings and process to combine. Let it stand and chill before serving. Flavor will mellow as horseradish matures.