Try this to get the newest set of files in CARstaging directly:
items 1 of (it, files of folders "c:\CARstaging") whose(item 1 of it contains item 0 of it) of (year of it as string & month of it as two digits & day_of_month of it as two digits) of (date (local time zone) of it) of maximum of modification times of files of folders "c:\CARstaging"