Do you mean something like this:
Code:
dialog charlist {
  size -1 -1 15 11
  option dbu
  combo 1, 0 0 15 150, size drop result
  button "&OK",2, 0 14 15 25,OK
}
on *:dialog:charlist:init:*:{
  var %i = 33
  while (%i < 256) { did -a $dname 1 $chr(%i) | inc %i }
  did -c $dname 1 1
}
?