If you have enabled Macro Virus protection (Tools | Macro | Security...) in Excel, if you add our macros to one of your workbooks, the next time you open the workbook you will see a message, like this;
C:\Windows\Personal\Book1.xls contains macros
You can choose Disable Macros or Enable Macros or More Info.
You should choose Enable Macros to allow workbooks which contain our macro module to calculate bar codes.
If you wish to prevent macro virus warnings, see the following section in the Microsoft Excel Help files;
Signing macro projects
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