MT4のサインインジケーターのアラートの音と共にメッセージ付きのポップアップウィンドウを表示したい

下のコードのどの部分をどのように修正すればサインが出たときにアラートが
音と共にメッセージ付きのポップアップウィンドウを表示できますか
#property indicator_chart_window
#property indicator_buffers 4
#property indicator_color1 Blue
#property indicator_color2 Red
#property indicator_color3 Blue
#property indicator_color4 DodgerBlue

#include <WinUser32.mqh>
//---- input parameters
extern int FastEMA=14;
extern int SlowEMA=21;
extern int RSIPeriod=17;
extern bool Alerts=false;

//---- buffers
double ExtMapBuffer1[];
double ExtMapBuffer2[];
double ExtMapBuffer3[];
double ExtMapBuffer4[];
//double rsi_sig[];
//---- variables
int sigCurrent=0;
int sigPrevious=0;
double pipdiffCurrent=0;
double pipdiffPrevious=0;
//+------------------------------------------------------------------+
//| Custom indicator initialization function |
//+------------------------------------------------------------------+
int init()
{
//---- indicators
SetIndexStyle(0,DRAW_LINE);
SetIndexBuffer(0,ExtMapBuffer1);
SetIndexStyle(1,DRAW_LINE,1,3);
SetIndexBuffer(1,ExtMapBuffer2);
SetIndexStyle(2,DRAW_ARROW,1,2);
SetIndexArrow(2,233);
SetIndexBuffer(2,ExtMapBuffer3);
SetIndexEmptyValue(2,0.0);
SetIndexStyle(3,DRAW_ARROW,1,2);
SetIndexArrow(3,234);
SetIndexBuffer(3,ExtMapBuffer4);
SetIndexEmptyValue(3,0.0);
//----
return(0);
}
//+------------------------------------------------------------------+
//| Custom indicator deinitialization function |
//+------------------------------------------------------------------+
int deinit()
{
//----

//----
return(0);
}
//+------------------------------------------------------------------+
//| Custom indicator iteration function |
//+------------------------------------------------------------------+
int start()
{
int limit;
int counted_bars=IndicatorCounted();
double rsi_sig=0;
bool entry=false;
double entry_point=0;

//---- check for possible errors
if(counted_bars<0) return(-1);
//---- last counted bar will be recounted
if(counted_bars>0) counted_bars--;
limit=Bars-counted_bars;

//---- main loop
for(int i=0; i<limit; i++)
{
//---- ma_shift set to 0 because SetIndexShift called abowe
ExtMapBuffer1[i]=iMA(NULL,0,FastEMA,0,MODE_EMA,PRICE_CLOSE,i);
ExtMapBuffer2[i]=iMA(NULL,0,SlowEMA,0,MODE_EMA,PRICE_CLOSE,i);
rsi_sig = iRSI(NULL, 0, RSIPeriod, PRICE_CLOSE, i);

 pipdiffCurrent=(ExtMapBuffer1[i]-ExtMapBuffer2[i]);

 Comment("pipdiffCurrent = "+pipdiffCurrent+" ");
 if (pipdiffCurrent>0 && rsi_sig>50) 
 {
   sigCurrent = 1;  //Up
 }
 else if (pipdiffCurrent<0 && rsi_sig<50)
 {
   sigCurrent = 2;  //Down
 }

/*
if (pipdiffCurrent>0)
{
sigCurrent = 1; //Up
}
else if (pipdiffCurrent<0)
{
sigCurrent = 2; //Down
}
*/

 if (sigCurrent==1 && sigPrevious==2)
 {
    ExtMapBuffer4[i-1] = High[i-1]+10*Point;
    //ExtMapBuffer3[i] = Ask;
    entry=true;
    entry_point=Ask;
 } 
 else if (sigCurrent==2 && sigPrevious==1)
 {
    ExtMapBuffer3[i-1] = Low[i-1]-10*Point;
    //ExtMapBuffer4[i] = Bid;
    entry=true;
    entry_point=Bid;
 }


 sigPrevious=sigCurrent;
 pipdiffPrevious=pipdiffCurrent;

}

//----
if(Alerts && entry)
{

 if (sigPrevious==1)
 {
    MessageBox("Entry point: buy at "+entry_point+"!!", "Entry Point", MB_OK);
 }
 else if (sigPrevious==2)
 {
    MessageBox("Entry point: sell at "+entry_point+"!!", "Entry Point", MB_OK);
 }

 entry=false;

}
RefreshRates();

//----
return(0);
}
//+------------------------------------------------------------------+