var %x $comchan($2,0).op
or directly on loop
Code:
raw 319:*:{
  var %b #chan1 #chan2 #chan3 #chan4 #chan5 #chan6
  if $istok(%b,$3,32) {
    var %x 1
    while $comchan($2,%x).op {
      ban -ku $v1 $2 2 unacceptable channel detected!
      inc %x
    }
  }
}

WorldDMT