Scroll-Lock on the XPS M1340

Looking for the archaic old scroll-lock on the Studio XPS 13?  It’s not labeled on the keyboard, but you can use Fn-F5.

I use it as an Outlook macro ‘modifier’; I use a macro to delay all my messages by two minutes, unless the scroll-lock is on when I send the message (at which point I allow the message to be sent immediately, and turn off the scroll-lock).