function  calculateUnits() {
  var volume = eval(document.getElementById('form1').volume.value)
  var content = eval(document.getElementById('form1').alccontent.value)
  var units = volume*content/1000
  document.getElementById('form1').units.value=custRound(units,1);
}

function custRound(x,places) {
  return (Math.round(x*Math.pow(10,places)))/Math.pow(10,places)
}