Why my NamePipe does not work?

From the post "http://www.forexfactory.com/showthread.php?t=125117", I was inspired with the idea to use namepipe to communicate with Excel.
However, when I run the following script in MT4, I always receive an alert "CreateNamedPipe failed". What did I do wrong?

//+------------------------------------------------------------------+
//|                                                   PipeServer.mq4 |
//+------------------------------------------------------------------+

#define PIPE_TYPE_MESSAGE 4
#define PIPE_READMODE_MESSAGE 2
#define PIPE_WAIT 0
#define PIPE_ACCESS_DUPLEX 3
#define PIPE_UNLIMITED_INSTANCES 255
#define NMPWAIT_USE_DEFAULT_WAIT 0
#define INVALID_HANDLE_VALUE -1
#define ERROR_PIPE_CONNECTED 535

#import "kernel32.dll"
        int CreateNamedPipeA(string PipeName,int dwOpenMode,int dwPipeMode,int nMaxInstances,int nOutBufferSize,int nInBufferSize,int nDefaultTimeOut,int lpSecurityAttributes);
        int ConnectNamedPipe(int hPipe,int lpOverlapped);
        int ReadFile(int hPipe, int& inBuffer[],int NumberOfBytesToRead, int& bytesRead[], int lpOverlapped);
        int WriteFile(int hPipe, string sBuffer, int NumberOfBytesToWrite, int& bytesWritten[], int lpOverlapped);
        int FlushFileBuffers(int hPipe);
        int DisconnectNamedPipe(int hPipe);
        int CloseHandle(int hPipe);
#import

string lastMessage="";
extern string Pipe = "Pipe1";

int start()
{
        string PipeName = "\\\\.\\pipe\\"+Pipe;
        int PipeMode = PIPE_TYPE_MESSAGE|PIPE_READMODE_MESSAGE|PIPE_WAIT;
        int hPipe = CreateNamedPipeA(PipeName,PIPE_ACCESS_DUPLEX,PipeMode,PIPE_UNLIMITED_INSTANCES,1024,1024,NMPWAIT_USE_DEFAULT_WAIT,NULL);
        if (hPipe == INVALID_HANDLE_VALUE) {
                Alert("CreateNamedPipe failed");
        return (-1);
        }
        while(!IsStopped())     {

                Comment("Pipe server ready ...\nSend \"STOP\" to stop server\n",lastMessage);
                bool fConnected = ConnectNamedPipe(hPipe, NULL) != 0;
                if(!fConnected)
                        fConnected = GetLastError() == ERROR_PIPE_CONNECTED;
                        
                if (fConnected) {
                        int inBuffer[256];
                        int bytesRead[1];
                        bool fSuccess = ReadFile(hPipe,inBuffer,4*ArraySize(inBuffer),bytesRead,NULL) !=0;
                        if (!fSuccess || (bytesRead[0] == 0)) break;
                        string inString="";
                        for(int i=0; i<bytesRead[0]; i++)
                                inString = inString + CharToStr( (inBuffer[i/4] >> ((i & 3)*8)) & 0xff);
                        lastMessage = "Last message from client: "+inString;
                        string outString = "Received ["+inString+"]";
                        int bytesWritten[1];
                        fSuccess = WriteFile(hPipe,outString,StringLen(outString)+1,bytesWritten,NULL) != 0;
                        if (! fSuccess || bytesWritten[0] != StringLen(outString)+1) break;
                        if(inString=="STOP") {
                                Comment("Pipe server stopped.");
                                FlushFileBuffers(hPipe);
                                DisconnectNamedPipe(hPipe);
                                CloseHandle(hPipe);                             
                                return(0);
                        }                       
                }
                FlushFileBuffers(hPipe);
                DisconnectNamedPipe(hPipe);
        }       
        CloseHandle(hPipe);                     
        return(0);
}