This isn't working in a full-screen application...

Keys.SendInput({shift_hold})

Apparently there is no SendSystemKeys "shift hold".

But (I just noticed after all these years) looks like "ShiftKey() ButtonClick()" is an efficient way to send a mouse click while holding the shift key down. 

is this a game by any chance? Some games intentionally read from very low level interfaces to avoid bots and other cheating things.

I would try and see if you can get AutoHotkey to work (it has quite a few different modes for sending keystrokes) for this usage. If so, you can either directly call AutoHotkey from Vocola or have it translate a different keystroke appropriately.

FWIW...

That probably was a strategy game. Instead of considering it cheating, I always considered strategy game makers lacking for not including click and keystroke saving macro recorders. I *loved* Warcraft 2 (NWTR/NWTH) way back when, without macros, probably where my RSI came from...

I use AutoHotkey a little. Got some amazing technical help from their forum.