The TreeView_GetExpandingNode() function returns the ID of the node that is being expanded in a tree view field.
TreeView_GetExpandingNode(tree_view_field)
• tree_view_field – The tree view field containing the node being expanded.
A long integer containing the node ID of the node being expanded. The value TV_NODEINVALID is returned if no node is being expanded.
This function is typically used only in the expand script for a tree view field to retrieve the ID of the node being expanded.