Hi S#,
No you don't have to *.
There's a reason why I've pointed to the compiler release (which I don't own, therefore I don't know if a predefined scheduled script will be compiled 1:1 and runs the way you expect it). This script should run without any scheduling options.
I haven't identified any reason why your script isn't working with the RUN WHEN (Macro Properties) settings.
So this was an idea

how to do it
if you own the compiler release.

And by the way - do you ?
300 sec are 5 min

, so if you want to check for that file every five minutes, that's a damn loop look-a-like

Why not keeping the script alive!
I assume you don't have to shut down the PC for 4,54 min. inbetween
E.
*as my grandma said "the only thing you have to do is, to die - sometimes"