Open random file in a folder (and include exceptions) - in batch

i'd like to create a batch file for opening a random file within a folder and all of it's subfolders.

I'd also like to add "exception folders" - folders, which are excluded from the random opening.

Currently, i'm using this:

@echo off
setlocal

:: Create numbered list of files in a temporary file
set "tempFile=%temp%\%~nx0_fileList_%time::=.%.txt"
dir /b /s /a-d %1 | findstr /n "^" >"%tempFile%"

:: Count the files
for /f %%N in ('type "%tempFile%" ^| find /c /v ""') do set cnt=%%N

call :openRandomFile

:: Delete the temp file
del "%tempFile%"

exit /b

:openRandomFile
set /a "randomNum=(%random% %% cnt) + 1"
for /f "tokens=1* delims=:" %%A in (
  'findstr "^%randomNum%:" "%tempFile%"'
) do start "" "%%B"
exit /b

It works perfectly for the random opening, but i'm not sure how i could exclude some of the subfolders within the specific directory.

Thank you in advance for your help! :)