I have a feeling that no matter what you do your in for a considerable delay, I had a thought of using a hidden window whcih well loaad 140000 lines in seconds if even that. Then a filter to put the lines into the dialog, I tested it with a small amount of data first to get it going, 1400 (1/100th), and something I noticed when changing to the large file, it accessed slower outright, ie: if it took 2 seconds to do 1400 when only 1400 were there, it took 6 seconds to do it when 140000 were there, I was thinking of ways around this, and thought i better test to make sure i was right about it going slowwer, so I just repeatedl;y loaded the same 100 lines of a 100 line hidden window into the dialog, and what i saw made me realize there are far more problems involved than just accessing the data to put in quickly, The big problem was , as more and more lines were added to the dialog, the time to add each 100 slowed down.

In the end i used this
Code:
alias testit {
  set %f c:\bigfile.txt
  set %ticks $ticks
  dialog -m big big
  var %c = $floor($calc($lines(%f) / 1000 + 1))
  timeraddline %c 0 addline $!calc( %c - $!timer(addline).reps)
  timer
}
;
alias addline {
  var %t = $ticks
  loadbuf $+($calc($1 * 1000 - 999),-,$calc($1 * 1000)) -o big 1 %f
  echo -st Doing $+($calc($1 * 1000 - 999),-,$calc($1 * 1000)) . Ticks taken so far $calc($ticks - %ticks) , this pass $calc($ticks - %t)
}


I used filename c:\bigfile.txt, but you could change that
If u run this you well see how the time to complete each 1000 line pass increases, dramaticly by the end of the file.

PS: i do acknoledge that as this moves down the file, the loadbuf command takes longer anyway, since it must read further down the file, however when i did a loadbuff to a window instead of a dialog, each pass was still well under 1 second, while the loadbuf to a dialog was taking 20 odd seconds each pass near the end.


Conclusion. Its only ever going to get So fast and thats that. Just loading the dialog slows the more you add.