function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode > 31 && (charCode < 48 || charCode > 57))
            return false;

         return true;
      }
function wp()
{
var d = document.form1.d.value;
var b = document.form1.b.value;
if(( d=="" && b=="")||( d=="" || b==""))
{
alert("please enter value for all fields");
}
else
{
var a= 4*3.14;
var d=d*d;
var l=a*d*b;
document.form1.l.value=a*d*b;
}
}