I've got a single vertex buffer and an index buffer for a cube in Directx9. I now want to generate a LPD3DXMESH  object from them, so that I can manage mouse picking and other stuff with the cube model. How can I achieve this? Here's the code of my vertex and index buffers:

	CUSTOMVERTEX vertices[] =
    {
        { -3.0f, 3.0f, -3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { 3.0f, 3.0f, -3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { -3.0f, -3.0f, -3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { 3.0f, -3.0f, -3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { -3.0f, 3.0f, 3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { 3.0f, 3.0f, 3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { -3.0f, -3.0f, 3.0f, D3DCOLOR_XRGB(0, 0, 0), },
        { 3.0f, -3.0f, 3.0f, D3DCOLOR_XRGB(0, 0, 0), },
    };

    d3ddev->CreateVertexBuffer(8 * sizeof(CUSTOMVERTEX),
                               0,
                               CUSTOMFVF,
                               D3DPOOL_MANAGED,
                               &vertex_buffer,
                               NULL);

    VOID* pVoid;
    vertex_buffer->Lock(0, 0, (void**)&pVoid, 0);
    memcpy(pVoid, vertices, sizeof(vertices));
    vertex_buffer->Unlock();

    short indices[] =
    {
        0, 1, 2,
        2, 1, 3,
        4, 0, 6,
        6, 0, 2,
        7, 5, 6,
        6, 5, 4,
        3, 1, 7,
        7, 1, 5,
        4, 5, 0,
        0, 5, 1,
        3, 7, 2,
        2, 7, 6,
    };

    d3ddev->CreateIndexBuffer(36 * sizeof(short),
                              0,
                              D3DFMT_INDEX16,
                              D3DPOOL_MANAGED,
                              &index_buffer,
                              NULL);

    index_buffer->Lock(0, 0, (void**)&pVoid, 0);
    memcpy(pVoid, indices, sizeof(indices));
    index_buffer->Unlock();