asterisk users - May 2005 - Correctly handle two extensions for the same phone (one with voicemail one without)

I find a need to have 2 extensions for the same phone. WIP 5000.
The reason is one extension needs voicemail the other extension does not
as I want to SendText() to that extension and I dont want voicemail to
answer and my SendText() be lost due to voicemail answering.

How is that accomplished?

If it was just in extensions.conf that is OK I can do that - but it is 
not as
I use the outgoing spool call file to originate the sendtext() call.

Thanks,

Jerry