I don't have version 6.21 and I know that the highlight feature was moved into the address book.

Maybe you should upgrade to the latest version. Here's a way to do it in 6.31.

Code:
alias sendkeys {
  var %object = sendkeys $+ $ticks
  .comopen %object WScript.Shell
  if ($com(%object)) { .comclose %object $com(%object,SendKeys,3,bstr,$1-) }
}

alias highlight { 
  sendkeys $+(%,tb)
  sendkeys $+(%,n)
  sendkeys {ENTER}
  echo -a Highlight is now $iif($highlight == $false,on.,off.)
}


It flashes suddenly because it opens up the dialog, checks/uncheks option and closes it again. I'm sure there'll be an actual command one day though.. smile