function catCheck(chcb) {
    var max = 3;

    var tblObj=document.getElementById("ctl00_CheckBoxList1");
    var chkObjlst= document.getElementById('ctl00_CheckBoxList1').getElementsByTagName("INPUT");
    var Cont = 0;
    for(i = 0; i < chkObjlst.length; i++) {
        if (chkObjlst[i].type == "checkbox" != -1 && chkObjlst[i].checked) {
            Cont++;
        } 
    }
    if (Cont < max) disableCatCheckGroup(false);
    else disableCatCheckGroup(true);
}
function disableCatCheckGroup(flag) {
    var tblObj=document.getElementById("ctl00_CheckBoxList1");
    var chkObjlst= document.getElementById('ctl00_CheckBoxList1').getElementsByTagName("INPUT");

    for(i = 0; i < chkObjlst.length; i++) {
        if (chkObjlst[i].type == "checkbox" != -1 && !chkObjlst[i].checked) {
            chkObjlst[i].disabled = flag;
        }
    }
}