Monitor mousewheel events of a patcher window. If switched on, the external reports the mousewheel scroll direction and delta together with the modifier state and the cursor position in the patcher. Until switched off, the scrollbars of the patcher won't receive mousewheel events.
It is only allowed to create one instance of the external per patcher and the patcher has to own a window. (doesn't work in bpatcher) Together with the [hover] object, it is easy to control the wheel monitoring when the cursor is on our target objects (see helpfile).