AutoSplit value based on Policy name

My goal is to have diferent log files which names are unique for each policy name. Is this possible?

Path and filename of log file:

D:\KIWI\Logs\Syslog-%PolicyName.txt

Syslog message:

source-address="10.18.100.100" source-port="62394" destination-address="10.17.200.100" destination-port="443" policy-name="263" source-zone-name="Trust" destination-zone-name="Untrust"

How should I define  %PolicyName?