Allow users to create a generic OOO message.

Separately, they could record the time frame they will be out of the office.

This would (conceivably) allow them to record one message for reuse.

Example:
You have reached the voice mail for Veronica Lee.

I will be out of the office from [variable-Start Date] to [variable End Date].

I you need immediate assistance, please contact the Help Desk.

If your request requires my personal attention, please leave a detailed message and I‘ll get back to you when I return to the office.