Whatever I created and lost yesterday was probably the answer to all
True, that's probably a bit too much for the average user! But there might be a simpler solution as well:
#series_index_string = {series_index:0>4s}
and then use that #series_index_string with the switch...
{#series_index_string:switch(00\d\d,0000-0099,01\d\d,0100-0199,)}
That way you don't need to manually change any columns... (I tested it, it works).