def write_number(row, col, num, format=nil)
record = 0x0203
length = 0x000E
xf_index = XF(row,col,format)
raise MaxSizeError if row >= RowMax
raise MaxSizeError if col >= ColMax
@dim_rowmin = row if row < @dim_rowmin
@dim_rowmax = row if row > @dim_rowmax
@dim_colmin = col if col < @dim_colmin
@dim_colmax = col if col > @dim_colmax
header = [record,length].pack("vv")
data = [row,col,xf_index].pack("vvv")
xl_double = [num].pack("d")
if BigEndian
xl_double.reverse!
end
append(header,data,xl_double)
end