The export will write all list items in the current view to the
spreadsheet. Once exported, Excel 2003 can sync both ways. This ability
was lost in the RTM version of Excel 2007 but I understand that there is
some kind of update that will restore this functionality.
So, create a list view that has what you want to see in the spreadsheet
and then export it. From that point on, periodically synchronizing the
spreadsheet with the list should do the trick.