Picked this up from Eli's blog:
In Excel 2003 you were able to sync amendments both from a Excel 2003 spreadsheet to a SharePoint List and from a SharePoint List to an Excel 2003 spreadsheet. But in Excel 2007 this is no longer the case...Well it was until Microsoft released an Excel 2007 Add-in.
This is a must install if you are upgrading to Office 2007 from Office 2003, otherwise your users will cry. The Excel 2007 Add-in, can be downloaded from: http://www.microsoft.com/downloads/details.aspx?FamilyID=25836e52-1892-4e17-ac08-5df13cfc5295&DisplayLang=en There is also an accompaning MSDN article "Publishing and Synchronizing Excel 2007 Tables to SharePoint Lists": http://msdn2.microsoft.com/en-us/library/bb462636(office.11).aspx