Code C/C++ :
#include <windows.h>
HHOOK hMsgBoxHook;
//-----------------------------------------------------------------------------
LRESULT CALLBACK MsgBoxProc(int nCode, WPARAM wParam, LPARAM lParam)
{
if(nCode == HCBT_ACTIVATE) SetDlgItemText((HWND)wParam, IDOK, "Fin");
return CallNextHookEx(hMsgBoxHook, nCode, wParam, lParam);
}
//-----------------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrev, PSTR lpszArg, int iCmdShow)
{
hMsgBoxHook = SetWindowsHookEx(WH_CBT, MsgBoxProc, 0, GetCurrentThreadId());
MessageBox(0, "Message ...", "Titre", MB_OK | MB_ICONINFORMATION);
UnhookWindowsHookEx(hMsgBoxHook);
return 0;
}