Get client hostname at "Security Level Rules"

We are attempting to establish a dynamic Security Level Rule that applies when the hostname of a client is found in a dataset.

This Rule is working:


But when we try to replace the static string 'clientHost' with {[System]Client/Network/Hostname} or {} it does not work.

Look at Security Zones:

Okay, in this case, I would have to write down all hostnames manually. Is there an option to retrieve these names from a database or a tag?