Guess this is javascript.

Similar as in excel, (I have seen this before), lets say I have 3 fields in a form.

Now when entering a numeric value in field 1, and lets say field 2 has the value of 5, then the value of field 1 times field 2 has to display in filed 3.

Please if anyone could assist me with this.

Do you just mean entering them into text boxes and you want PHP to add them up whenever you submit?

This would be a javascript version

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<script language="javascript" type="text/javascript">
function calcFields()
{
	if(!IsNumeric(document.getElementById("txtVal1").value) || document.getElementById("txtVal1").value == "")
	{
		var val1 = 0;
	}
	else
	{
		var val1 = document.getElementById("txtVal1").value;
	}
	document.getElementById("txtVal1").value = val1;
	if(!IsNumeric(document.getElementById("txtVal2").value) || document.getElementById("txtVal2").value == "")
	{
		var val2 = 0;
	}
	else
	{
		var val2 = document.getElementById("txtVal2").value;
	}
	document.getElementById("txtVal2").value = val2;
	
	document.getElementById("txtVal3").value = parseFloat(val1) + parseFloat(val2);
}

function IsNumeric(sText)
{
	var ValidChars = "0123456789.";
	var IsNumber=true;
	var Char;
	
	
	for (i = 0; i < sText.length && IsNumber == true; i++) 
	{ 
		Char = sText.charAt(i); 
		if (ValidChars.indexOf(Char) == -1) 
		{
			IsNumber = false;
		}
	}
	return IsNumber;
}
</script>
</head>

<body onload="calcFields();">
<table cellpadding="0" cellspacing="0">
	<tr>
		<td>&nbsp;</td>
		<td><input type="text" name="txtVal1" id="txtVal1" onblur="calcFields();" /></td>
	</tr>
	<tr>
		<td>+</td>
		<td><input type="text" name="txtVal2" id="txtVal2" onblur="calcFields();" /></td>
	</tr>
	<tr>
		<td colspan="2"><hr style="width:100%;" /></td>
	</tr>
	<tr>
		<td>=</td>
		<td><input type="text" name="txtVal3" id="txtVal3" readonly="readonly" /></td>
	</tr>
</table>
</body>
</html>
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