\label{Spreadsheet_Export_Row}

The export row determines what information is passed to the next higher
spreadsheet in the spreadsheet hierarchy 
(\ref{Spreadsheet_Hierarchy}).  
The first 26 columns of the row, labeled ``A-Z'', are
exported.  The remaining 26 columns, labeled ``a-z'', 
are not and may be used for supporting computations.  
The export row is row number 0.