This will be true whether it uses the cloud or not. Excel worksheets can already have external links (both on the Web and to other files). If those web resour

This will be true whether it uses the cloud or not. Excel worksheets can already have external links (both on the Web and to other files). If those web resources or other files aren't available, you're out of luck! And the older ones may only open on software that no longer runs on modern machines. This is why it's important to restore your backups once in a while, or in this case, validate your critical files.