function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
       if (charCode!=46 && charCode!=8 && (charCode < 48 || charCode > 57))
            return false;

         return true;
      }
function bl()
{
var v1= document.form1.v1.value;
var m1= document.form1.m1.value;
var m2 = document.form1.m2.value;
if((v1=="" && m1=="" && m2=="" )||(v1=="" || m1=="" || m2=="" )) 
{
alert("please enter value for all fields");
}
else
{
var w =v1*m1;
var r = (w/m2);
var v = (w/m2);
document.form1.v.value=(w/m2);
var cc = (eval(v)-eval(v1));
document.form1.cc.value=(eval(v)-eval(v1));
}
}