How to validate if radio button option ==4 and date2.disabled==false ,,,,
alert message Duration option not available


Code:
function checkForm(TheForm) {
        //if((document.example.opt2.value==4) && (document.example.date2.value != "yyyy-mm-dd")){
        //      var msg="select only Start date, duration option not available";
        //      alert(msg);
        //      return false;
        //      }
        if (document.example.date2.disabled == true) {
                if (document.example.date1.value == "yyyy-mm-dd") {
                        var msg = "date not chosen from calendar icon";
                        alert(msg);
                        return false;
                }
        }
        else{
                if (document.example.date1.value == "yyyy-mm-dd" || document.example.date2.value == "yyyy-mm-dd") {
                        var msg = "start or end date not chosen from calendar icon";
                        alert(msg);
                return false;
                }
                if(document.example.date1.value > document.example.date2.value){
                        var msg = "choose proper date-Start date is greater than end date";
                        alert(msg);
                        return false;
                }
                 if(document.example.date1.value == document.example.date2.value){
                        var msg = "choose proper date-Start and end date is equal";
                        alert(msg);
                        return false;
                }

        }
}


<FORM NAME="example" class="frm" onSubmit="return checkForm(this); submit=”a.php”>

  <input type="radio" name="opt2" value="2" checked>
  Option 1<br><br>
  <input type="radio" name="opt2" value="3">
  Option 2<br><br>
  <input type="radio" name="opt2" value="4">
  Option 3<br><br>