Code:
Alias Away {
  if $1 == back {
    away
    ame is Back from : ( $+ %away.msg $+ ) Gone For : ( $+ $duration($awaytime) $+ )
    nick %away.bnick
  }
  elseif $1 == away {
    set %away.bnick $me
    ame is Away. Reason : ( $+ %away.msg $+ )
    away %away.msg
    nick %away.anick
  }
  elseif (!%away.anick) || !%away.msg {
    set %away.anick $$?"What Nick do you want to change into when you go away?"
    set %away.msg $$?"What is your away reason?"
  }
  elseif ($away == $true) {    .scon -at1 away back  }
  else {    .scon -at1 away away  }
}


Untested, but based on your initial code.