automatic tasks with encrypted volumes

[Jody2020]

Hi, may be some can help me with this:

I'm using a FS6712x and created an encrypted volume.
I now want to unmount this encrypted volume automatically every night @ midnight with an automatic task.
So, here are my questions:
is it possible to start scripts with a cronjob on the device and wich commands and parameters do I need to unmount the encrypted volume?

Thanks in advance and please apologize my lousy english!
Regards
Jody2020