The TreeView_GetFirstChild() function returns the ID of the first child node for the specified parent node in a tree view field.
TreeView_GetFirstChild(tree_view_field, node_ID)
• tree_view_field – The tree view field containing the parent node.
• node_ID – A long integer specifying the ID of the parent node.
A long integer containing the node ID of the first child of the specified parent node. If the specified node contains no children, the TV_NODEINVALID constant is returned.