Kurt:
The cheapest, simple way to do what you want is as follows: You must have availabel tip ring (analog) ports off your switch. To these ports attach 2 or 3 DIGITAL answering machines set to ANNOUNCE ONLY, and on them record your primary announcement. If you need a secondary announcement set up another port with another answering machine. These answering machines are on the order of $30 each, or of course you couild go to Avaya and get a 4 port digital announcement unit for a few thousand, .... !