Code:
alias CheckIdlers {
 var %chan = [color:red]$1[/color], %a = $nick(%chan,0)
 while %a {
  if ($ulevel != 10) || ($ulevel != 11) {
   if ($nick(%chan,%a).idle > 20) {
    ban -ku300 %chan $nick(%chan,%a) 2 Please do not idle. Return in a while if you need help or want to help
  }
 }
dec %a
 }
}
This should work. Note that the usage of the alias is /checkidlers #channel, so $1 is the identifier for the channel name in that alias. The var %chan has to be set to $1 then.

Hope this works!

Zyzzy. smile