# File lib/spreadsheet/worksheet.rb, line 416
   def XF(row, col, xf=nil)
      if xf.kind_of?(Format)
         return xf.xf_index
      elsif @row_formats.has_key?(row) 
         return @row_formats[row].xf_index
      elsif @column_formats.has_key?(col)
         return @column_formats[col].xf_index
      else
         return 0x0F
      end
   end