How can I specify the selected value in collection_select when fieldname different than variable?

Hi all,
  I have a relatively simple scenario. I have a form that can have a
list of multiple phone objects in it. I'm trying to get the edit and
entry screens to work with unique field names. I have entry and
record creation working, but I'm still working on edit. Is it
possible for me to specify the value of the selected index to the
"collection_select" method via an option or html option? I read the
doc, but I can't find what I'm looking for. Below is my code, as you
can see my field and select names are "phone_#" where # is the
iteration index, but the actual variable is "phone".

Main form snippet

n = 0
for phone in @phones do
fieldname = "phone_#{n}";
<tr><td>Number:</td><td> <%= text_field_tag fieldname, phone.number%></

<td><%= get_phone_types fieldname%></td></tr>

n += 1

helper with get_phone_types