When you format a worksheet, you can use the Format Painter tool to quickly copy the formatting from one area of the worksheet to another. However, if you make changes to the original area, the changes won't be copied to the other areas. To protect your worksheet's formatting:

1. Select the cells that contain the formatting you want to protect.
2. On the Home tab, in the Styles group, click Format as Table.
3. Click a table style.
4. Click OK.

The selected cells will be formatted as a table, and the formatting will be protected. If you make changes to the original cells, the changes will be copied to all cells in the table.