Checkboxlist Checked Event Client Side Using JavaScript

<script type="text/javascript"> 

function CheckBoxChecked(ChkID) {
            var status = false;
            var CheckBoxID = document.getElementById('<%=chkHvecYes.ClientID%>');
            if (CheckBoxID.checked == true){
            status=true;
                return status;}
            else {
                alert('Please Select CheckBox');
                return status;
            }

        }

//chkHvecYes  is checkboxlist Id

function SeletedTab() {         
            var checkBoxArray = document.getElementById('<%=chkIso_action.ClientID%>').getElementsByTagName('input');          
                var checkBoxRef = checkBoxArray[5];     // for 7th Item in the checkboxlist

                if (checkBoxRef.checked) {
document.getElementById('plock').style.display = "block";
 document.getElementById('plock').style.visibility = "visible";
                }

else
                    document.getElementById('plock').style.display = "none";document.getElementById('plock').style.visibility = "hidden";
           
        }

</script>

<p id="plock">

  Checkboxlist Checked Event or Onclick Client Side Using JavaScript

</p>

<asp:CheckBoxList  ID="chkIso_action" runat="server" onclick="SeletedTab() ">

<asp:ListItem Text="Test1" Value="0">

<asp:ListItem Text="Test1" Value="1">

<asp:ListItem Text="Test1" Value="2">

<asp:ListItem Text="Test1" Value="3">

<asp:ListItem Text="Test1" Value="4">

<asp:ListItem Text="Test1" Value="5">   

</asp:CheckBoxList >

<asp:Button runat="server" Text="Submit" ID="btnHSubmit" OnClientClick="CheckBoxChecked(this)"></asp:Button>