Hii Nalla!!
plz check
<script>
function getValue()
{
theAnswer = ((document.form1.number2.value - document.form1.number1.value) / document.form1.number1.value * 100);
alert(theAnswer)
}
</script>
<form name=form1>
Number1<input type=text name=number1><br>
Number2<input type=text name=number2>
<br>
<input type=button onclick="getValue()" value="calculate" name=number22>
</form>

hope this will help you


Cheers :)

vinod