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

         return true;
      }
function yw()
{
var ga = document.form1.ga.value;
var gt = document.form1.gt.value;
if((ga=="" && gt=="")||(ga=="" || gt==""))
{
alert("please enter value");
}
else
{
var a = ga/gt;
var b = 1-a;
var c = b * 100;
document.form1.e.value=b * 100;
}
}