AJAX help - proper use of remote_function

Hi.

I'm having a hard time understanding how to use remote_function().

Here's what I want to do:

I have two divs. The one on the left lists criteria names. When the
user clicks on one of the entries in the listbox on the left, I want
to make a remote call to the server to populate the right div based on
several things: the name of the criteria on the left, and a serialized
list of the names+selections of the other criteria.

For example, assume the left list is like this:

Continent
Country
State
City

When the user clicks on Continent, I should send a request to the
server like /reports/get_criteria_options

The result will go into a hidden div called crit_continent. It will
hold a series of checkboxes and text labels.

The more complicated case is when the user clicks City. I want it to
send a request like this - /get_criteria_options?
list=city&continent=1,3,4&country=2

I can manually (JavaScript) create the query string, but that may not
even be necessary given the power of Prototype. In any case, part of
my confusion is knowing how to even define the remote_function call
from within my template.

Here's what I have right now, as an example (and it doesn't work
right)

<%= remote_function :update => 'crit_city',
                                   :url => { :action =>
'get_criteria_options' },
                                   :with => "$H({list:
$F('crit_city'), country: $F('crit_country'), state:
$F('crit_state')}).toQueryString()" %>

Unfortunately that results in an error (according to Firebug):
Form.Element.Serializers[method] is not a function

Googling that error, I see comments about duplicate IDs. I don't
think I have dup ids...

I'm very interested in any help or comprehensive non-trivial
examples. Barring that, I may be open to short-term actual help for
pay.

Thanks much!
Michael

<%= remote_function :update => 'crit_city',
                                  :url => { :action =>
'get_criteria_options' },
                                  :with => "$H({list:
$F('crit_city'), country: $F('crit_country'), state:
$F('crit_state')}).toQueryString()" %>

Unfortunately that results in an error (according to Firebug):
Form.Element.Serializers[method] is not a function

Probably means that one of those 3 elements (crit_city etc...) is not
an input element (or something similar like a select or a textarea).
It certainly seems suspicious to me that the thing you are updating
('crit_city') has the same id as something you are submitting, as you
had said previously that the point of the exercise was to populate a
div (which implies that that is what the element with id crit_city is)

Fred