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>