<script type="text/javascript">
    function is()
    {
    if(document.getElementById("RadioYes").checked==true)
    {
    alert("YES");
    document.getElementById('BtnUpLoad').disabled=document.getElementById('RadioYes').checked; 
    }
    else if(document.getElementById("RadioNo").checked==true)
    {
    alert("NO");
    document.getElementById('BtnUpLoad').disabled=document.getElementById('RadioYes').checked;
    }
    }
    </script>

<asp:RadioButton  ID="RadioYes" runat="server" Text="同意" onclick="is()" /> 
                              <br /> 
                            <asp:RadioButton  ID="RadioNo" runat="server" Text="不同意" onclick="is()"/>