Evaluator test for dual lister with something selected

Help & Support
1

I confess to being totally at sea with evaluator clauses. What should I specify to show a button if the current lister is dual and at least one file is selected. My hack (below) does not work.

@showif:=selfiles>1 && dual

2

Try

@showif:=selfiles>1 && IsChecked("Set DUAL=on")