Getting an alert

Hi!

I am tying to program a simple indicator that would giv me an alert box when certain conditions are true

For example send an alert when price closes over a 20 day moving avreage

I cant get it to work tho ( no alert are popping up)

Can anyone point out whats wrong with the code?

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using System.Runtime.InteropServices;

namespace cAlgo.Indicators
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC)]
    public class FortunaSignal : Indicator
    {
        [DllImport("user32.dll", CharSet = CharSet.Unicode)]
        public static extern int MessageBox(IntPtr hWnd, String text, String caption, uint type);

        [Parameter(DefaultValue = 0.0)]
        public double Parameter { get; set; }



        private SimpleMovingAverage mma;


        protected override void Initialize()
        {

            mma = Indicators.SimpleMovingAverage(MarketSeries.Close, 20);


        }


        public override void Calculate(int index)
        {

            if (MarketSeries.Close[index] < mma.Result[index - 1])
            {

                DisplayAlert("Buy signal");
            }

            else if (MarketSeries.Close[index] > mma.Result[index - 1])
            {

                DisplayAlert("Sell signal");

            }

        }


        protected void DisplayAlert(string tradyTypeSignal)
        {


            var alertMessage = string.Format("{0} {1} {2} {3} {4}", tradyTypeSignal, Symbol.Code);

            MessageBox(new IntPtr(0), alertMessage, "Trade Signal", 0);

        }
    }


}