Jak sprawdzić czy zmieniła się pozycja w ComboBox (WinAPI)

Na bazie szablonu z Dev C++ (gotowiec)

#include <windows.h>

/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

/*  Make the class name into a global variable  */
char szClassName[ ] = "WindowsApp";

int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nFunsterStil)

{
    HWND hwnd;               /* This is the handle for our window */
    MSG messages;            /* Here messages to the application are saved */
    WNDCLASSEX wincl;        /* Data structure for the windowclass */

    /* The Window structure */
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    wincl.style = CS_DBLCLKS;                 /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;                 /* No menu */
    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default color as the background of the window */
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           "Windows App",       /* Title Text */
           WS_OVERLAPPEDWINDOW, /* default window */
           CW_USEDEFAULT,       /* Windows decides the position */
           CW_USEDEFAULT,       /* where the window ends up on the screen */
           544,                 /* The programs width */
           375,                 /* and height in pixels */
           HWND_DESKTOP,        /* The window is a child-window to desktop */
           NULL,                /* No menu */
           hThisInstance,       /* Program Instance handler */
           NULL                 /* No Window Creation data */
           );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nFunsterStil);

    /* Run the message loop. It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND cb_handle = 0;
    static int pozycja_3 = 0;
    switch (message)                  /* handle the messages */
    {
        case WM_CREATE:
             //tworzymy combo boxa
             cb_handle = CreateWindowEx(0,"COMBOBOX","",WS_CHILD | WS_VISIBLE | WS_VSCROLL | CBS_DROPDOWNLIST,20,20,150,22*4,hwnd,NULL,((LPCREATESTRUCT)lParam)->hInstance,NULL);
             //i zachowujemy uchwyt, lepsza metoda jest pod numerze komponentu - tu jednak dla uproszczenia

             //i dodajemy kilka pozycji
             SendMessage(cb_handle, CB_ADDSTRING,0, (LPARAM)"1");
             SendMessage(cb_handle, CB_ADDSTRING,0, (LPARAM)"2");
             pozycja_3 = SendMessage(cb_handle, CB_ADDSTRING,0, (LPARAM)"3");
             SendMessage(cb_handle, CB_ADDSTRING,0, (LPARAM)"4");
             //send message zwraca nam numery pozycji. UWAGA inserty i delety moga nam to zmienic !
             //w tej kolejnosci bedzie OK jesli nic nie zmienimy ! Lepiej rozpoznawac po wartosci.

             break;
        case WM_COMMAND:
             //rozpoznajemy czy nasz komponent wyslal jakis komunikat.
             //Rozpoznajemy go po uchwycie (mozna po ID jak wspomnialem WM_CREATE)
             //My czekamy na to, az user skonczy wybieranie danej pozycji, odpowiada za to komunikat
             //CBN_SELENDOK.

             if (lParam == (LPARAM)cb_handle && HIWORD (wParam) == CBN_SELENDOK)
             {
                 //jesli wybor sie zmienil to sprawdzamy jaka aktualnie
                 //pozycja jest wybrana
                 int iIndex = SendMessage(cb_handle, CB_GETCURSEL, 0, 0);
                 //i jesli to pozycja 3 wyswietlamy komunikat
                 if (pozycja_3 == iIndex)
                 {
                         MessageBox(hwnd,"Jupiiiii pozucja 3 zaznaczona !","", 0);
                 }
             }
             break;
        case WM_DESTROY:
            PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
            break;


        default:                      /* for messages that we don't deal with */
            return DefWindowProc (hwnd, message, wParam, lParam);
    }

    return 0;
}