function isaPosNum(s) {
   return (parseInt(s) > 0)
}

function qty_check(item, min, max) {
   var returnVal = false
   if (!isaPosNum(item.value)) 
      alert("Please enter valid number(s)")
   else if (parseInt(item.value) < min) 
      alert("Please enter a " + item.name + " of at least " + min)
   else if (parseInt(item.value) > max) 
      alert("Please enter a " + item.name + " up to " + max)
   else 
      returnVal = true
   return returnVal
}