Is there any way to find all the cells in a worksheet/workbook that use a
particular style? I can only think of looping over all cells but that will
be far too slow for the size of workbooks I have.

The problem I have is that I want to be able to change the number format on
all cells that have the Total style. The Total style though doesn't include
a number format currently, and instead will be either a number or percentage
depending on how the user has configured it. I need to update the decimal
places used in the cells, so was going to write a tool to look at all cells
with the Total style.