I would like to write code sorting the entire spreadsheet, excluding headers,
by first sorting column I to put all topics together in descending order and
then adding an empty row at the end of each topic to separate them. My
topics are just 3 values and they are

Stationary
Posters
Books

Then my next sort is to isolate each topic and sort each topic individually
by column D ascending. Col D is a currency value.

The end result would be each topic in column I would be sorted by ascending
dollar value in Col D

This spreadsheet is updated each day so the row count is unknown. Is this
even possible?