For Approvals tasks, you can specify a reviewer to replace a reviewer who is out of the office. You can also set these display options:
Select Preferences in the left frame, or select File, and then Preferences.
Click the Planning icon, and then select Application Settings.
Under Approvals Options, select Yes to set these display preferences:
Optional: Click the link for the Out of Office Assistant to set up an alternate budget reviewer while the current reviewer is out of the office, or to reset reviewer responsibilities when the reviewer returns. See Selecting an Alternate Reviewer.