Actually, you can select the field in a text box, right click, and format it. However, here's a better way of doing percentages.
1. Put the number field on the report.
2. Right-click and format.
3. On the Number tab, click on the Customize button.
4. On the Number tab, set the number of decimal places.
5. On the Currency Symbol tab, Enable the currency symbol, Set the Position to the right side of the number, and change "$" to "%".
This will give you the percent sign without having to use a text box.
-Dell