Gregorio,

If you have the handle of a parent window then you can use the EnumChildWindows API function. As this function requires an application-defined callback function the example is in C but could easily be incorporated into a VFP FLL. If you need to find the ID associated with the child control then you can use the Spy++ tool that comes with VS.

#define ID_FIRSTCHILD  100 
#define ID_SECONDCHILD 101 
#define ID_THIRDCHILD  102 
 
LONG APIENTRY MainWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) 
{ 
    RECT rcClient; 
    int i; 
 
    switch(uMsg) 
    { 
        case WM_CREATE: // creating main window  
 
            // Create three invisible child windows. 

            for (i = 0; i < 3; i++) 
            { 
                CreateWindowEx(0, 
                               "ChildWClass", 
                               (LPCTSTR) NULL, 
                               WS_CHILD | WS_BORDER, 
                               0,0,0,0, 
                               hwnd, 
                               (HMENU) (int) (ID_FIRSTCHILD + i), 
                               hinst, 
                               NULL); 
            }
 
            return 0; 
 
        case WM_SIZE:   // main window changed size 
 
            // Get the dimensions of the main window's client 
            // area, and enumerate the child windows. Pass the 
            // dimensions to the child windows during enumeration. 
 
            GetClientRect(hwnd, &rcClient); 
            EnumChildWindows(hwnd, EnumChildProc, (LPARAM) &rcClient); 
            return 0; 

        // Process other messages. 
    } 
    return DefWindowProc(hwnd, uMsg, wParam, lParam); 
} 
 
BOOL CALLBACK EnumChildProc(HWND hwndChild, LPARAM lParam) 
{ 
    LPRECT rcParent; 
    int i, idChild; 
 
    // Retrieve the child-window identifier. Use it to set the 
    // position of the child window. 
 
    idChild = GetWindowLong(hwndChild, GWL_ID); 
 
    if (idChild == ID_FIRSTCHILD) 
        i = 0; 
    else if (idChild == ID_SECONDCHILD) 
        i = 1; 
    else 
        i = 2; 
 
    // Size and position the child window.  
 
    rcParent = (LPRECT) lParam; 
    MoveWindow(hwndChild, 
               (rcParent->right / 3) * i, 
               0, 
               rcParent->right / 3, 
               rcParent->bottom, 
               TRUE); 
 
    // Make sure the child window is visible. 
 
    ShowWindow(hwndChild, SW_SHOW); 
 
    return TRUE;
}

Regards
Neil