Use the * wildcard rather than the & wildcard in your event
Code:
on *:text:!test*:#:{
  var %a = 1, %b = $0
  while %a <= %b {
    echo -a Word %a is $($+($,%a),2)
    inc %a
  }
}


This will simply echo in your active screen what is typed when someone else types !test <other words>

Please note that the above will trigger for any combination that starts with !test
Thus !testing 1 2 3 would trigger the code as well as !test 1 2 3