Yes, you can format an entire workbook all at once using the "Format Painter" tool in Excel. Here are the steps to follow:

1. Open the workbook that you want to format.
2. Go to the first sheet in the workbook and format it the way you want it to look.
3. Select a cell or range of cells that have the formatting you want to copy.
4. Click on the "Format Painter" button in the "Clipboard" group on the "Home" tab.
5. The cursor will change to a paintbrush icon. Click and drag the paintbrush over the cells you want to apply the formatting to.
6. Release the mouse button to apply the formatting to the selected cells.

Repeat steps 3-6 for each sheet in the workbook that you want to format. This will save you a lot of time compared to formatting each sheet individually.