Disclaimer: this could be terrible advice. It may be a workaround until a better solution comes around. Any old forum posts I found basically said 'if youre using setkey, theres probably a better way', but that's because the questions were pretty vague.
You'll still have to pagedown after but..
Code
setkey [keyname] [state]
bind PAGEUP down setkey RCTRL down
bind PAGEUP up setkey RCTRL up
Note, found a solution to my issue which was "F8 is in a terrible place for quick targetting of monsters". This also fixed my original solution which was binding TAB to "input /targetbnpc". Trying to hit TAB after calling a /magic <stnpc> macro would just throw an error.
Code
bind %TAB setkey F8 down; wait 0.3;setkey F8 up
I needed a replacement for Tab functionality, so I reconfigured some other keys in-game
Code
Menu > Config > Misc. 2 >
Keyboard Size: "Compact 1"
[Q] Menu/Target Cursor Left
[E] Menu/Target Cursor Right