Yes, it is possible via AA.

Default Auto-Attendant Script aa.aef

The default auto-attendant script provided with Cisco Unity Express is named aa.aef. This file resides in the system directory, and cannot be downloaded, copied, or uploaded. This default auto-attendant application is also known as the "system script" or "system AA." This default script supports basic functions such as dial-by-extension, dial-by-spelling username, and call operator functions. If additional functionality is required, then you must create a customized auto-attendant script.

The aa.aef script supports holiday lists and business-hours schedules. When a call reaches the auto attendant, the system checks if the current day is a holiday. If it is, the system plays a holiday prompt called AAHolidayPrompt.wav, which states "We are closed today. Please call back later." The script then executes the next operation in the script.

If the current day is not a holiday, the system checks if the business is open or not. If the business is open, the system plays the AABusinessOpen.wav prompt, which is an empty file. If the business is closed, the system plays the AABusinessClosed.wav prompt, which states "We are currently closed. Please call back later."

Following are the parameters that may be configured for the aa.aef script:

?welcomePrompt?default: AAWelcome.wav

?operExtn?default: none

?holidayPrompt?default: AAHolidayPrompt.wav

?businessOpenPrompt?default: AABusinessOpen.wav

?businessClosedPrompt?default: AABusinessClosed.wav

?businessSchedule?default: systemschedule

?disconnectAfterMenu?default: false

?allowExternalTransfers?default: false

This URL should help you:

http://www.cisco.com/en/US/products/sw/voicesw/ps5520/products_administration_guide_chapter09186a0080874e2e.html