I have a situation where i'd like to monitor sales for a 3rd party
telephone number and I'd like a 3rd party to monitor telephone sales I
drive to them.

I have a technology to change a web site before it's presented to the
user.  If the merchant is a catalog, i am able to change the phone
number to my own phone number.  I'd also like to apply this proxy
method to the telephone.

I would like to do one of 3 things:

1) Have the merchant set up an 800# number for my customers.  My
customers would call my 800# number, but they'd be seamlessly
transferred to the merchant's normal telephone center.  The purpose of
my 800# number is to more easily track phone sales.  Is it easy for
major catalog companies to set up an 800# number, and attribute all
sales that come through that number to a 3rd party (ie, me)?  Is this
a standard offering in advanced telephone services?  Approximately how
much does this cost?

2) I could also replace the phone number with one of my own that would
present the user w/ different options.  If 5-10 merchants, the user
could press 1-10 for the merchant they want to be connected.  Once
selected, the user would be passed on to the normal 800# line.  This
would allow me to track the call volume.  Who offers these types of
services?  Approximately how much do they cost.

3) I could use a combination of 1 & 2.  I create my own 800# and pass
the user to the merchant's 800# for me.  I could track the number of
calls made, and the merchant could track sales from my line.  This
gives me a checks & balance.

4) Anything else i should consider?  

thanks,
Tec