Enable macros in Office 2007
In older versions of Excel, you could allow macros using the Tools menu (Options, Security tab, Macro Security button).
Office 2007 is totally different from 2003 and earlier versions. Here is the link to their help document detailing how to enable macros to run without the prompt (Enable all macros).
Enable or disable macros in Office documents
Basically, they moved the security settings from the Tools / Options menu to the new Trust Center.
