Two Autocompletes, make first value affect the second

I have two text_field_with_auto_complete
text_field_with_auto_complete :user, :state
text_field_with_auto_complete :user, :suburb

The user fills in the text_field_with autocomplete… but then I want to
filter the results in the suburb with the value they’ve just entered
def auto_complete_for_user_suburb
@suburbs = PostCode.find(:all,
:conditions => [“lower(locality) LIKE ?”, ‘%’ +
params[:user][:suburb].downcase + ‘%’
AND state LIKE “WHATS IN STATE FEILD”
],
:order => ‘locality ASC’,
:limit => 12)

render :partial => 'suburbs'

end

my problem is that I can’t work out a way of delivering the text_field
:state contents to the auto_complete_for_user_suburb function.

Any ideas?