ButtonNotebook

ButtonNotebook[ ] gives the notebook, if any, that contains the button which initiated the current evaluation.

ButtonNotebook returns a NotebookObject.

If a button in a palette initiates evaluation in another notebook, then ButtonNotebook[ ] will be the palette, but EvaluationNotebook[ ] will be the other notebook.

If the current evaluation was not initiated by a button, then ButtonNotebook[ ] will return $Failed.

See The Mathematica Book: Section 2.10.3.

See also: Notebooks, EvaluationNotebook, SelectedNotebook, InputNotebook.