IAT hook using C++ dll by inject not intercepts api

Question

I'm trying make a hook in MessageBoxA api in a remote process made by me using IAT hook tecnique. I'm using Process Hacker software for inject my dll file into my process and until here works fine.

My unique trouble is that MessageBoxA never is intercepted when i will call this api from my application.

I have discovered that this api don't can be found in table of import of my process.

So, i want know any suggestion about how i can find this api on table.

Here is code that i use:

#include <windows.h>
#include <string.h>
#include <stdio.h>

void HookFunction(char* funcName, LPDWORD function);
LPDWORD FoundIAT(char* funcName);

int WINAPI HookMessageBoxA(HWND hWnd, LPCTSTR lpText, LPCTSTR lpCaption, UINT uType);  

BOOL APIENTRY DllMain (HINSTANCE hInstance, DWORD dwReason, LPVOID lpReserved) 
{
    if(dwReason == DLL_PROCESS_ATTACH)
    {
        MessageBox(NULL, "Injeted with success!", "Hello", NULL);
        HookFunction("MessageBoxA", (LPDWORD)&HookMessageBoxA);
    }
    return TRUE;
}

void HookFunction(char* funcName, LPDWORD function)
{
    LPDWORD pOldFunction = FoundIAT(funcName);

    DWORD accessProtectionValue , accessProtec;

    int vProtect = VirtualProtect(pOldFunction, sizeof(LPDWORD), PAGE_EXECUTE_READWRITE, &accessProtectionValue);

    *pOldFunction = (DWORD)function;

    vProtect = VirtualProtect(pOldFunction, sizeof(LPDWORD), accessProtectionValue, &accessProtec);
}

int WINAPI HookMessageBoxA(HWND hWnd, LPCTSTR lpText, LPCTSTR lpCaption, UINT uType)
{
    return MessageBoxA(hWnd, "Hello", "DLL answering here!", uType);
}

LPDWORD FoundIAT(char* funcName)
{
    DWORD test = 0;

    LPVOID pMapping = GetModuleHandle(NULL);

    if (pMapping == NULL)

        exit(-1);

    PIMAGE_DOS_HEADER DosHeader = (PIMAGE_DOS_HEADER) pMapping;

    if (DosHeader->e_magic != IMAGE_DOS_SIGNATURE)

        exit(-1);

    PIMAGE_NT_HEADERS NtHeaders = (PIMAGE_NT_HEADERS) ((char*) DosHeader + DosHeader->e_lfanew);

    if (NtHeaders->Signature != IMAGE_NT_SIGNATURE)

        exit(-1);

    PIMAGE_DATA_DIRECTORY DataDirectory = &NtHeaders->OptionalHeader.DataDirectory[1];

    PIMAGE_IMPORT_DESCRIPTOR ImportDescriptor = (PIMAGE_IMPORT_DESCRIPTOR) ((char*) DosHeader + DataDirectory->VirtualAddress);

    PIMAGE_THUNK_DATA32 OriginalFirstThunk = (PIMAGE_THUNK_DATA32)((char*) DosHeader + ImportDescriptor->OriginalFirstThunk);

    while(OriginalFirstThunk != 0)
    {
        DWORD name = (DWORD)((char*) pMapping + ImportDescriptor->Name);

        OriginalFirstThunk = (PIMAGE_THUNK_DATA32)((char*) DosHeader + ImportDescriptor->OriginalFirstThunk);

        PIMAGE_THUNK_DATA32 FirstThunk = (PIMAGE_THUNK_DATA32)((char*) DosHeader + ImportDescriptor->FirstThunk);

        while(OriginalFirstThunk->u1.AddressOfData != 0)
        {
            PIMAGE_IMPORT_BY_NAME NameImg = (PIMAGE_IMPORT_BY_NAME)((char*) DosHeader + (DWORD)OriginalFirstThunk->u1.AddressOfData);

            test = (DWORD)OriginalFirstThunk->u1.Function & (DWORD)IMAGE_ORDINAL_FLAG32;

            if (test == 0)
            {
                if(strcmp(funcName, (const char*)NameImg->Name) == 0)
                {
                    MessageBox(NULL, NameImg->Name, "", NULL);
                    return (LPDWORD)&(FirstThunk->u1.Function);
                }
            }
            OriginalFirstThunk++;
            FirstThunk++;
        }
        ImportDescriptor++;
    }
    return 0;
}

Source

EDIT 1:

I have seen with more datails, that now this code is able to find MessageBoxA api :D, but still when i'll call this api from my application (made in Delphi), the hook don't work. :-(

My Delphi code here:

procedure TForm1.btn1Click(Sender: TObject);
begin
 MessageBoxA(Application.Handle, 'Delphi application here!', 'Hello',0);
end;

EDIT 2:

This can be a definitive solution, but link is offline. Someone can help me about how it can be adapted to my code above please?