Subgroups by using the IIF expressions

I'm trying to organise my ScreenConnect Subgroups by using the expressions but on the true statement I'm unable to achieve what I'm after

IIF (GuestOperatingSystemName LIKE '*server*', ('!Servers', CustomProperty2) , CustomProperty2 )

https://docs.connectwise.com/ConnectWise_ScreenConnect_Documentation/Get_started/Host_page/Session_groups/Create_session_subgroups

Could someone be kind enough to point me in the right direction!

This works fine but I also need to include CustomProperty2 at the end of the true statement.

 IIF (GuestOperatingSystemName LIKE '*server*', '!Servers' , CustomProperty2 )

Thanks,

Tom