Can't Synchronize Excel List with Sharepoint

[TommyVee]

I have a Sharepoint list (2003) to which I create a linked Excel (2003)
spreadsheet. As long as the spreadsheet exists on my local drive, I am able
to synchronize changes with the underlying Sharepoint list OK (or visa
versa). Now I upload this exact same spreadsheet to a Sharepoint document
library. I open it up and make changes as usual. But now, when I try to
synchronize, the "Synchronize List" menu item is grayed out. I know I can
ask the user to update the underlying Sharepoint list directly, but I need
the updates in the spreadsheet, e.g., for formatting. What is wrong and why
doesn't this work?

Thanks in advance, TommyVee