The NoBot control

I'm very unsure about the code for NoBot that I have. Is this code reasonable that it could work or has a missed something

<asp:NoBot ID="NoBot1" runat="server" CutoffMaximumInstances="3"
           CutoffWindowSeconds="10"  ResponseMinimumDelaySeconds="10"
            OnGenerateChallengeAndResponse="NoBot1_GenerateChallengeAndResponse" />

 protected void NoBot1_GenerateChallengeAndResponse(object sender, AjaxControlToolkit.NoBotEventArgs e)
        {
            NoBotState state;
            NoBot1.IsValid(out state);

            if (state.ToString().ToLower() != "valid")
               lblError.Text = state.ToString();
        }

//Tony