PostMessage + GetMessage

bool ret;
    MSG msg;
    while((ret = GetMessage(&msg, NULL, 0, 0)))
    {
        cout << "Reading...\n";
        if (ret != -1)
        {
            cout << "Got " << msg.message << ".\n";
        }
        else { cout << "End...\n"; getch(); }
    }

    HWND h;
    h = FindWindow(NULL, "C:\\Users\\Uhehesh\\Documents\\RAD Studio\\Projects\\Debug\\Project8.exe");
    if(h == 0) h = FindWindow(NULL, "test");
    if(h == 0) cout << "Error.\n";
 
    PostMessageA(h, WM_USER + 1, 0, 0);
    cout << "Sent to " << GetForegroundWindow();
 
    getch();