Depending upon the level of security that is set within Microsoft Excel it may mean that you are unable to run spreadsheets which have used Visual Basic. To check your excel security settings:

Open Excel
Go to the "Tools" Menu
Go to Macro
Macro

Go to Security
Excel Security

If your security level is set to "high", it is unlikely that you will be able to run spreadsheets which use VB. Instead you can lower the security to Medium. If you set the security setting to Medium, every time a spreadsheet is loaded it will ask whether to enable or disable Macros.