function isNumberKey(evt)
      {
	 var charCode = (evt.which) ? evt.which : event.keyCode
	 if (charCode !=8 && (charCode < 45 || charCode > 57))
            return false;

         return true;
	}

function cub()
{
var a = document.form1.a.value;

var b = document.form1.b.value;

if((a=="" && b=="") ||(a=="" || b==""))
{
alert("please enter value for all fields");
}
else
{
var c = a*a*a;
document.form1.c.value=c;
var d = b*b*b;
document.form1.d.value=d;
document.form1.e.value = (eval(c)+eval(d));
}
}