asterisk users - Sep 2005 - Caller ID, Attended Transfers, Polycom

We have contracted with an outside call center to provide sales for a
certain product.  We want to be able to transfer people over to those
dedicated sales agents using an attended transfer (so we can prepare them
with as much information as we have), to a regular extension.  So far, so
good.  All of this is working just great.  

We want the caller's information presented as the CallerID so that the
outside staff can use the information for tracking the calls.  When the call
leg is created that starts the transfer sequence, the CallerID is set to our
outgoing CallerID by the Polycom phone.  Are there any good tricks to
determine how to set it, such that it will match the caller ID of the number
that called?