Here's a tip from Ken Williams, Ruekert & Mielke.

Ever have the CEO or your boss ask to be able to see everyone’s timesheets and expense reports? If this is all they need access to, grant them this right by making them an “accounting manager” in their employee setup (first screen check box). By checking this box, you allow the person to see all timesheets and expense report in the Manage time and expense function. There is no need to create other special security options for specific people, and they can then filter to see specific employees and time frames as they wish.