JavaScript Real Time Calculation

I've been around looking for javascript that can do Real Time Calculation.
javascript real time calculation, javascript real time calculation textbox.
by some lucky keywords i found this code. this is exactly the code that i want. it really do the real time calculation. and it doesn't need onChange or OnBlur function.
Just try it

Example

+

=

this is the javascript code
<script type='text/javascript' >
function startCalc(){
  interval = setInterval("calc()",1);
}
function calc(){
  one = document.autoSumForm.firstBox.value;
  two = document.autoSumForm.secondBox.value;
  document.autoSumForm.thirdBox.value = (one * 1) + (two * 1);
}
function stopCalc(){
  clearInterval(interval);
}
</script>
this is the html code

<form name="autoSumForm">
 
<input class="right" type=text name="firstBox" value="" onFocus="startCalc();" onBlur="stopCalc();"><br>
+ <input class="right" type=text name="secondBox" value="" onFocus="startCalc();" onBlur="stopCalc();"><br>
= <input class="right" type=text name="thirdBox">
</form>

thanks to this site javascript.internet.com . i finally found something useful. almost forgot its Created by: Jim Stiles | www.jdstiles.com