Grrr! Hee hee, sorry that doesn't get old (for me at least. I'm sure it does for you).

What you're looking for isn't actually under out of office reply (which is universal) but instead under Rules / Alerts (Tools --> Rules and Alerts)

Use these handy steps:
[list:1u17e3ik]
Create a new rule.
Select blank rule.
Check messages when they arrive.
From people or distribution list.
Select the people you want to reply to.
Click Next.
check box for 'have server reply using a specific message'
Click the 'a specific message' link.
Fill in your text.
Click 'Save and Close'
Save your rule and turn it on.
....
PROFIT (wait, wrong process)
[/list:u:1u17e3ik]

I'd test it first, but that seemed to work for me.

--Zig