For Excel 2007 or 2010:
1.  Go to File, Options (For 2007 click the Office button then Excel Options)
2.  Click Trust Center
3.  Click Trust Center Settings...
4.  Click Add-ins
5.  If Require Application Add-ins to be signed by a Trusted Publisher is marked then Excel does require application add-ins to be signed by a Trusted Publisher.
* Under Trusted Publishers F9 will show under Issued To as "Infor Global Solutions, Inc" or "Infor Enterprise Solutions Holdings, Inc"
 
For Excel 2003:
1.  Go to Tools, Macro, Security
2.  The Security Level tab will specify whether or not Excel will allow add-ins from untrusted sources.  If this is set to High or Very High the F9 add-in will need to have a current digital certificate.
3.  To check the certificate go to the Trusted Publishers tab in this Window.  F9 will show under Issued To as "Infor Global Solutions, Inc" or "Infor Enterprise Solutions Holdings, Inc" with an expiration date.