Eanble Disable control on checkbox click

<script type="text/javascript">
        function EnableControl(val) {
            var sbmt = document.getElementById("<%=btnSubmit.ClientID %>");
            if (val.checked == true) {
                sbmt.disabled = false;
            }
            else {
                sbmt.disabled = true;
            }
        }
       
       
    </script>
<div style="float: left;">
            <asp:CheckBox ID="chkAgree" runat="server" Text="I Agree" onclick="EnableControl(this)"
                Checked="false" />&nbsp;&nbsp;&nbsp;
            <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" /></div>