# File lib/spreadsheet/worksheet.rb, line 337
   def write_url(row, col, url, string=url, format=nil)
      record = 0x01B8
      length = 0x0034 + 2 * (1+url.length)
      
      write_string(row,col,string,format)

      header = [record, length].pack("vv")
      data   = [row, row, col, col].pack("vvvv")

      unknown = "D0C9EA79F9BACE118C8200AA004BA90B02000000"
      unknown += "03000000E0C9EA79F9BACE118C8200AA004BA90B"

      stream = [unknown].pack("H*")

      url = url.split('').join("\0")
      url += "\0\0\0"

      len = url.length
      url_len = [len].pack("V")

      append(header + data)
      append(stream)
      append(url_len)
      append(url)
   end