Detecting click in Textarea vertical scrollbar

I’ve looked everywhere and can’t find out how to detect a mouse click in the vert. scrollbar of a textarea. I tried using the MouseDown event in the textarea and any clicks in the v. scrollbar go undetected.

I know I’ve done this in the past … just can’t remember how. Does the scrollbar have a name? I’m lost.

Windows 10/ current Xojo (2022 release 2)