Unmanaged C++ dll taking CString as parameter crashes my app!

[super_beda]

Hi DaniWeb team,
I had to import in .NET a DLL with a function that takes as input some CString arguments.
So I developed a little wrapper dll for this function containing an unmanaged function that takes as input some const char*,"translates" them into CString and then passes them to the original Dll in such a way than from my managed app in .Net I could import my little wrapper (using Dllimport and MarshalAs) and pass to it some "string" object.
The build of all goes ok, but when I run my .net app using it crashes when calling the unmanaged dll (I saw it in debugging mode).
This is my dll code:

#include "stdafx.h"
#include "UpdateTrigger.h"

#define MAXMODULE 50
typedef int (__stdcall *cfunc)(unsigned int, CString, CString);

 cfunc UpdateTriggerSlot;
 

#ifdef _MANAGED
#pragma managed(push, off)
#endif

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    return TRUE;
}
//

extern "C" __declspec(dllexport) int fnUpdateTriggerBridge(unsigned int dsp, const char* triglistURL, const char * trigorderlistURL)
{
    CString triglist(triglistURL);
    CString trigorder(trigorderlistURL);

    HINSTANCE hLib = LoadLibrary(_T("MSS_SDK.dll"));
    if(hLib==NULL) {

           return -1;
       }

       


      UpdateTriggerSlot =(cfunc)GetProcAddress((HINSTANCE)hLib, "DSP_UpdateTriggerSlot");
      

       if(UpdateTriggerSlot==NULL) {

           
            FreeLibrary((HINSTANCE)hLib);
            return -1;
       }

       int result = UpdateTriggerSlot(dsp, triglist, trigorder);

       FreeLibrary((HINSTANCE)hLib);

      

    return result;
}




#ifdef _MANAGED
#pragma managed(pop)
#endif

where MSS_SDK.dll is the other unmanaged dll containing the function taking CString as input.

I import it in C # like that:

[DllImport("UpdateTrigger.dll", EntryPoint = "fnUpdateTriggerBridge", CallingConvention = CallingConvention.Cdecl)]
        public static extern int _DSP_UpdateTriggerSlot(UInt32 dsphandle, [MarshalAs(UnmanagedType.LPStr)] string ListURL, [MarshalAs(UnmanagedType.LPStr)] string OrderListURL);

When I call this library from .NET the application crashes and an error pop-up appears, saying

Debug Error!

"Run-time check Failure #0: The file of ESP was not properly saved across a function call. This is usually a result of calling a function declared with one calling convention with a function pointer declared with a different calling convention"

What am I doing wrong?
Thanks in advance