条件後入れでウィンドウハンドルを取得できる「WindowExplorerクラス」をつくった ref: http://qiita.com/hirocueki/items/a7fcbadb7d7e562a60b5

file2.cpp

#include <functional>
typedef std::function<bool(HWND)> IsMatchedWindow;
typedef std::function<HWND(HWND)> GetMatchedWindow;

class WindowExplorer
{
public:
    static HWND Search(IsMatchedWindow _condition, GetMatchedWindow _getter = nullptr)
    {
        WindowCondition Condition(_condition, _getter);
        ::EnumWindows( EnumWindowsProc,  (LPARAM)&Condition );
        return Condition.GetHandle();
    }

private:

    class WindowCondition
    {
    private:
        HWND hFoundWnd;
        IsMatchedWindow IsMatchedWindow_;
        GetMatchedWindow GetMatchedWindow_;

    public:
        WindowCondition(IsMatchedWindow cond, GetMatchedWindow getter=nullptr)
            : IsMatchedWindow_(cond)
            , GetMatchedWindow_(getter)
            , hFoundWnd(nullptr)
        {}

        inline HWND GetHandle()const { return hFoundWnd; }
        bool found(HWND hwnd)
        {
            if ( IsMatchedWindow_(hwnd))
            {
                hFoundWnd = ( GetMatchedWindow_ )? GetMatchedWindow_(hwnd) : hwnd;
                return hFoundWnd != nullptr;
            }
            return false;
        }
    };

    static BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam )
    {
        WindowCondition* condition = reinterpret_cast<WindowCondition*>(lParam);

        if ( !condition )
            return FALSE;

        if ( condition->found(hwnd) )
            return FALSE;

        return TRUE;
    }
};

クラス名が”hoge”で子ウィンドウのクラス名が”fuga”

const auto class_is_hoge = [](HWND hwnd) -> bool {
        TCHAR buffer[MAX_PATH] = {0};
        ::GetClassName( hwnd,buffer,MAX_PATH );
        return _tcscmp(_T("hoge"), buffer) == 0;
};

const auto class_is_fuga = [](HWND hwnd) -> HWND {
    return ::FindWindowEx(hwnd, nullptr, _T("fuga"), nullptr);
};
const HWND hwnd = WindowExplorer::Search(class_is_hoge, class_is_fuga);

タイトルが”hello”をさがす

const auto title_is_hello = [](HWND hwnd) -> bool {
    TCHAR buffer[MAX_PATH] = {0};
    ::GetWindowText( hwnd,buffer,MAX_PATH );
    return _tcscmp(_T("hello"), buffer) == 0;
};

const HWND hwnd = WindowExplorer::Search(title_is_hello);