IF you receive files to inspect of you need to alter the file without making any changes to the original file, you can use the version option available in Excel 2003 and prior versions. However this option is no longer available in Excel 2007. Even if you use track changes, you might accidently end up saving all the changes in the original file. One trick you can try instead is to open the file as read only and be prompted to save the file using a different file name every time you use the [Ctrl] + [S] keyboard short cut. To do so, carry out the following steps:

~ Start Excel 2007 application.
~ Click the 'Office' button and select 'Open' from the left panel of the drop-down menu.
~ Browse for the file to be opened in the 'Read-only' mode in the 'Open' dialog box.
~ Click the drop-down arrow appearing near the 'Open' button of the dialog box.
~ Select the 'Open Read-Only' option.

The file opens as read-only.

Now if you save the file, you will have to proVide a different file name.