It is unlikely that err checking would repair the file.
analogkid2digitalman is dead right when he says, 'back up, and back up often!'
Fortunately, Excel provides a way to do so without having to repeatedly create a backup manually....
It is a good idea to save an file with the backup option set to ON.
Here's how it is done:
When you create a new file, you use 'Save As...' to save it with an identifiable name. In the SaveAs dialog box look for a button captioned 'Tools' or 'Options...' - click this and select the checkbox for 'Always create backup' in the Save Options dialog box that appears.
Once this option is set ON, whenever you next save the file, the last saved version gets saved as the backup file (extension .xlb) of the same name in the same folder. So if a file gets corrupt, you can always recall the xlb file of the same name and save as xls. This way the max you will lose is a single session of work. It is highly unlikely thet both the xlb (backup) and the xls (current version) will get corrupted at the same time.
Mala Singh
'Dare to Imagine'