Variable Extension to Invalid

Can’t seem to find an answer on this on forums/google. Is there a way to send a _XXX extension to an i extension.

So basically when the _XXX extension gets an input of three numbers, I have it play an audio file from a folder with the same three numbers. What I’m trying to do is have it go to my invalid (i) extension if they put in three digits that don’t correspond to a folder.
example:
exten => _XXX,1,Answer()
exten => _XXX,n,Playback(some/place/${EXTEN}/theAudio)

Is there something I could add next to the ${EXTEN} to have it make sure the folder exists and send to “i” if it doesn’t. Or is there a way to write out a list of the numbers (e.g.; 201,202,203) _XXX can accept and have it reference it and send calls to “i” if not on the list? I’m going to have a lot of folders with audio in them and I don’t want to add a written (not a pattern) extension for each one, but I need some kind of invalid for wrong entries. Currently when I call in, if I enter a wrong extension it just jumps over the audio part and hits a Goto that takes it back to a starting menu to enter another extension for _XXX.

Any thought?

GotIf and the function that returns the result of executing a shell script.