Change the number of the most recently used workbooks
To customize the Office Button menu, follow these steps:
1. Click the Microsoft Office Button , and then click Excel Options:
2. Choose the Advanced tab and then scroll down to the Display section:
3. In the Show this number of Recent Documents box, set the number of workbooks you want to have on the Office Button menu. You can choose any number between 0 and 50 (inclusive).
4. Click the OK button.
When you increase the number in the Show this number of Recent Documents dropdown list, Excel doesn't add the extra files immediately to the list on the Office Button menu, but rather adds them one by one as you open and close files.
If you reduce the number to 0, someone can't increase that number and immediately see which files you've been working with. (But they may be able to find that information elsewhere in the Windows operating system.)
To make Excel keep a particular workbook on the Office Button menu, open the menu, and then click the pin next to the file's name. Word pushes in the pin to indicate that the document is "pinned" in place, and then keeps the file in that place on the list until you unpin it by clicking the pin again.