Adobe Acrobat Pro JavaScript, using a trusted function, to access file system directory and list files in a folder not working

I want to list the files in a folder in a list box that the user can select from.  My trusted function code is:

myListFilesInFolder = app.trustedFunction(function(cFolderPath){

    app.beginPriv();

        var folder = Folder(cFolderPath);

        var files = folder.getFiles();

        var fileList = [];

        for (var i=0; i < files.length; i++) {

            if (files[i] instanceof File) {

            fileList.push(files[i].name);

        }

    }

    return fileList;

    app.endPriv();

});

The code to be run with a button in the PDF is:

var folderPath = "/c/temp/my_files";

var filesArray = myListFilesInFolder(folderPath);

if(filesArray && filesArray.length > 0) {
   app.alert("Files found:\n" + filesArray.join("\n"));
} else {
   app.alert("No files found or an error occurred.");
}

I get an error in the trusted function saying Folder not defined.  Need help on the button code too to show the files listed in a drop down or list box that my user can select from too.  I’m trying to cut and paste from examples I can find online, but haven’t been able to make this work.

WES