v-table index

Hi, everyone

I can operate with pointer-to-member functions.
How can I get virtual member function index from v-table?
I would like to iterate v-table and to execute virtual method by v-
table index.

Is it possible?

CODE:
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class ICollection
{
public:
    virtual void SystemMethod_0() = 0;
    virtual void SystemMethod_1() = 0;
    virtual void SystemMethod_2() = 0;
    virtual void SystemMethod_3() = 0;

    /* pointer-to-member */
    typedef void (ICollection::*fnMethod)();

    /* get pointer-to-member by id */
    virtual ICollection::fnMethod getMethodPtr(size_t nIndex) = 0;

    /* ctor and virtual dtor */
    ICollection() {}
    virtual ~ICollection() {}
};

class CTest: public ICollection
{
public:
    virtual void SystemMethod_0() {printf("SystemMethod_0");}
    virtual void SystemMethod_1() {printf("SystemMethod_1");}
    virtual void SystemMethod_2() {printf("SystemMethod_2");}
    virtual void SystemMethod_3() {printf("SystemMethod_3");}

    virtual ICollection::fnMethod getMethodPtr(size_t nIndex)
    {
        ICollection::fnMethod fnAction = NULL;
        switch(nIndex)
        {
        case 0: fnAction =
(ICollection::fnMethod)&CTest::SystemMethod_0;break;
        case 1: fnAction =
(ICollection::fnMethod)&CTest::SystemMethod_1;break;
        case 2: fnAction =
(ICollection::fnMethod)&CTest::SystemMethod_2;break;
        case 3: fnAction =
(ICollection::fnMethod)&CTest::SystemMethod_3;break;
        default: assert(false);break;
        }
        return fnAction;
    }

    /* ctor and dtor */
    CTest() {}
    ~CTest() {}
};

/* usage */
int main(int argc, const char* argv[])
{
    ICollection* pCollection = new CTest();

    ICollection::fnMethod fnAction = NULL;
    for (size_t nIndex=0; nIndex!=4; ++nIndex)
    {
        /* I would like to get v-table index and execute method by v-table
index */
                /* But I can operate only with pointer-to-memeber like
this */
        fnAction = pCollection->getMethodPtr(nIndex);
        (pCollection->*fnAction)();
    }

    delete pCollection;

        return 0;
}
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Thank you for helping me!