validation on nested datalist

<script language="javascript" type="text/javascript">
    function Validate(source, args) {
        var why;
        why = "";

//        for (var i = 1; i <= parseInt(document.getElementById('<%= dlDirectors.ClientID %>" + cntl + "_ddlDirectors').value); i++) {
        for (var i = 1; i <= 10; i++) {
        cntl = "";
        if (i < 10) {
            cntl = "_ctl0" + i;
        }
        else {
            cntl = "_ctl" + i;
        }
        var numclasseschanged = "<%= dlDirectors.ClientID %>" + cntl + "_ddlDirectors"
//        alert(document.getElementById(numclasseschanged).value)
        for (var m = 1; m <= parseInt(document.getElementById(numclasseschanged).value); m++) {
            cnt2 = "";
            if (m < 10) {
                cnt2 = "_ctl0" + m;
            }
            else {
                cnt2 = "_ctl" + m;
            }
            var surname = "<%= dlDirectors.ClientID %>" + cntl + "_DataList1" + cnt2 + "_director_surname"
            var givenname = "<%= dlDirectors.ClientID %>" + cntl + "_DataList1" + cnt2 + "_director_givenname"
            var howrelated = "<%= dlDirectors.ClientID %>" + cntl + "_DataList1" + cnt2 + "_director_howrelated"
            var perbenifit = "<%= dlDirectors.ClientID %>" + cntl + "_DataList1" + cnt2 + "_director_percentofbenifit"

            why += checkText(document.getElementById(surname))
            why += checkText(document.getElementById(givenname))
            why += checkText(document.getElementById(howrelated))
            why += checkText(document.getElementById(perbenifit))

        }
       }
        if (why != "") {

            alert("Please enter the fields marked in pink !");
            return args.IsValid = false;
        }
    }
    </script>