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