ใช้ function หา ผลรวมอัตโนมัติ จาก multi input แนะนำด้วยครับ

function fncCal()
{
	var sum = 0;
	for(i=1;i<=document.frmAdd.hdnLine.value;i++)
	{
		sum = sum + parseFloat( document.getElementsByName("boxc"+i).value);			
	}

        document.getElementsByName("sum1").value=sum;
}

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script language="javascript">
function fncCal()
{
	var tot = 0;
	var sum = 0;
	for(i=1;i<=document.frmAdd.hdnLine.value;i++)
	{
		tot = parseFloat("document.frmAdd.boxc"+i+".value");
		sum = sum + parseInt(tot.value);		
		document.frmAdd.sum1.value=sum;				
		
	}
}
</script>
<form action="" name="frmAdd" id="frmAdd" method="post">
<center>

<table width="50%" border="1">
<?php
  $line = 3;
  if($line == 0)
  {$line=1;}
  for($i=1;$line>=$i;$i++)
  {	
  $boxa=$_POST["boxa$i"];
  $boxb=$_POST["boxb$i"];
  $boxc= $boxa+$boxb;
  if(isset($_POST["save"]))
  {
	  echo"<script>alert('Your score :: $boxc')</script>";	  
  }
  ?>
  
 
  <tr>       
    <td width="10%" align="center">
    <input type="text" name="boxa<?php echo $i; ?>" size="20" value=""></td>
    <td colspan="3"  width="40%"align="center">
    <input type="text" name="boxb<?php echo $i; ?>" size="100%" value=""></td>
    <td colspan="2" width="20%" align="center">
    <input type="text" name="boxc<?php echo $i; ?>" size="20" style="background: #DBDBDB" OnChange="fncCal()"></td>
  </tr>
  <?php
  }
  ?> 
  <tr>   
    <td colspan="4" align="center">รวม</td>
    <td colspan="2" width="20%" align="center">
      <input type="text" name="sum1" size="20"  value="Your piont <?php  echo $boxc; ?>"style="background: #DBDBDB">
      <input type="submit" name="save" id="save" value="save">
    </td>
  </tr>
  </table>
  </center>
  </form>

function fncCal()
{
	var sum = 0;
	for(var i=1;i<=document.frmAdd.hdnLine.value;i++)
	{
		var boxc = document.getElementsByName("boxc"+i)[0];
		if(parseFloat(boxc.value)){
			sum += parseFloat(boxc.value);
		}
	}

        document.getElementsByName("sum1")[0].value = sum;
}