Microsoft's advance security bulletin has come out and it looks like they are planning on releasing 3 security bulletins on Tuesday, March 10, 2009. However, none are for the Excel malformed file issue that is currently being exploited. Of the patches, one is a critical rated remote code execution vulnerability. The other two are listed as spoofing and rated Important. The critical vulnerability appears to affect all production operating systems from Windows 2000 through Windows 2008. More information is available here:

Microsoft Security Bulletin Advance Notification for March 2009