Check out the ENVI 5 Help under 'batch'. You can also look at the ENVI Classic Help under the same heading. As for converting your *.las images to *.hdr... you probably want to convert that to an ENVI format either *.img or *.dat since the *.hdr file is just a plain text file that ENVI uses to open the associated image file. You can find out more about this through the ENVI Help.