C / C++ / MFC

// Start with the root item:
HTREEITEM hRoot = myTree.GetRootItem();

// Get the first child of the root:
HTREEITEM hChild1 = myTree.GetChildItem(hRoot);

// Move through the siblings until you reach the node you want:
HTREEITEM hChild2 = myTree.GetNextSiblingItem(hChild1)
HTREEITEM hChild3 = myTree.GetNextSiblingItem(hChild2)

HTREEITEM ItemFromIndex(int index)
{
    HTREEITEM item = m_tree.GetRootItem();
    while (item != NULL && index > 0)
    {
        item = NextTreeItem(item);
        --index;
    }
    // if item is not NULL, you now have the HTREEITEM of the given index
    return item;
}

HTREEITEM NextTreeItem(HTREEITEM hStartItem)
{
    HTREEITEM hItem = hStartItem;
    if (m_tree.ItemHasChildren(hItem))
    {
        // move down to next level
        HTREEITEM hChildItem = m_tree.GetChildItem(hItem);
        hItem = hChildItem;
    }
    else
    {
        bool foundSibling = false;
        while (!foundSibling && hItem != NULL)
        {
            // move along same level
            HTREEITEM hSiblingItem = m_tree.GetNextItem(hItem, TVGN_NEXT);
            if (hSiblingItem != NULL)
            {
                hItem = hSiblingItem;
                foundSibling = true;
            }
            else
            {
                // nothing on same level so move up and try again
                hItem = m_tree.GetParentItem(hItem);
            }
        }
    }
    return hItem;
}

while( !m_bStopPushThread )
{
   // Do whatever the thread is supposed to do
}