If you don't want your Excel files to be viewed by others, then you can set it password protection, use in the save file with the method of encryption can be used to achieve protection purposes, here to pay special attention to the password you set must remember, otherwise they will be considered illegal intruders and refused to enter. The specific ways to encrypt files are:
A, in the File menu bar, click Save or (Save As), enter a filename in the dialog box that pops up save or (save As);
B, then click the "General Options" button under the Tools bar in this dialog box, and enter your password in the "Save Options" dialog box that pops up.
Note here that it provides two layers of protection, if you also set the password to modify permissions, then even if the file is opened also need to enter the password to modify the permissions to modify.
C, click "OK" button, in the Pop-up Password confirmation window re-enter the password, and then click "Confirm", the last point "save" the completion of the encryption work. When you reopen the file, you require a password, and if the password is incorrect, the file will not open.