Updates

Excel 2003 Macro Security

When you change macro settings they are only changed for that particular Office program.
In 2003 the setting was universal across all the Office applications.

Very High - (Added in 2003). VBA macros will not run (regardless of whether they are signed or unsigned).
High - VBA macros will only run if they are from a trusted source and contain a recognised digital signature. Any macros that do not have a digital signature will not run. You will not receive a prompt. This is the default option.
Medium - VBA macros will only run if you choose the enable them. You will be asked if you want to enable or disable the macros before the file is opened. This was the default in Office 2000.
Low - Any file containing macros will run without the knowledge or approval of the user. Not recommended. Make sure you have third party anti-virus software installed on the PC.

Excel 2003 Trusted Sources

Trust all installed add-ins and templates - Allows VBA macros to run if they are stored in specific trusted locations. This is selected by default.
Trust Access to Visual basic project - (Added in 2002). Allows VBA macros to access the Visual Basic Project. This needs to be checked if you want to access the VBA Object model (i.e. code modules and userforms) from external code. This is not selected by default.

Excel 2003 Security Options