If you have a workbook that you've carefully organized — worksheets in a certain order, worksheet tabs named just so — you can protect that structure from being tampered with by using the Protect Workbook command.
On the Tools menu, point to Protection, and then click Protect Workbook. You can select the options to protect your workbook Structure and Windows.
When you protect the structure, worksheets can't be moved, deleted, hidden, unhidden, or renamed, and new worksheets can't be inserted.
When you protect windows, they'll appear the same size and position as you left them each time the workbook is opened.
Type a password for the workbook in the Password box. This does not encrypt the workbook contents, and it is optional. This password is not used to open the workbook; it's only used to unprotect the workbook if you decide to change the structure. If you don't supply a password, however, anyone will be able to unprotect the workbook.