DllMain Template to Execute Code in a .cpl File

// dllmain.cpp : Defines the entry point for the DLL application.
#include "pch.h"
#include <Windows.h>

extern "C" __declspec(dllexport) LONG CplApplet()
{
    MessageBoxA(NULL, "Replace this message box with something more interesting...", "Control Panel", 0);
    return 1;
}

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    switch (ul_reason_for_call)
    {
        case DLL_PROCESS_ATTACH:
        {
            CplApplet();
        }
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
    }
    return TRUE;
}