well if you still want the popup then you can do

alias massinvite {
  tokenize 32 $$?="Channel to invite?" $$?="New channel?"
  var %x = 1
  while (%x <= $nick($1,0,vr)) {
    if ($nick($1,%x,vr) != $me) invite $v1 $2
    inc %x
  }  
}