applying UI Policy only for specific user group

Hi,

how to write a filter condition based on current user group membership when applying UI policy.
the filter condition is: if current user is member of group X, then do apply some UI policy

I found a code snippet:
if(gs.getUser().isMemberOf(group_X_sys_id)){
//Do something...
}

but how do I put the code into the condition filter box?

Thank you