Filtering and sorting

Hi all, I am still kind of new to the Ruby scene, and have run into a
bit of a snag that I have been wrestling with all day. I have a Table
that has a form that you use to filter information, and then renders
the page again with the filtered information appearing in the table.
Each column is able to be sorted. However, if I try to sort once a
filter has been run, it defaults all the filter values to nil, and
sorts the entire database of records.

this is in my Controller currently, and will work one or the other,
but not both:
if request.post?
      scope = NewRecord.scoped({})
      scope = scope.conditions "file_bitrate = ?",
params[:file_bitrate] unless params[:file_bitrate] == '--Select
Bitrate--'
      scope = scope.conditions "file_quality = ?",
params[:file_quality] unless params[:file_quality] == '--Select
Quality--'
      scope = scope.conditions "file_samplerate = ?",
params[:file_samplerate] unless params[:file_samplerate] == '--Select
Sample Rate--'
      scope = scope.conditions "file_encoding = ?",
params[:file_encoding] unless params[:file_encoding] == '--Select
Encoding--'
      scope = scope.conditions "file_short = ?", params[:file_short]
unless params[:file_short] == '--Select Filename--'
      @new_records = scope
      if params[:new_codec] != '--Select Codec--'
        @new_records.reject!{|rec| rec.pair.run.new_codec !=
params[:new_codec]}
      end
    end

    @new_records ||= NewRecord.find(:all)
     if params[:sort_key]
        @new_records = @new_records.sort_by {|record|
record.send(params[:sort_key]) }
        if params[:sort_reverse]
          @new_records = @new_records.reverse
        end
    end

If anyone has any tips on how to keep the current values of the
filter, get the form to re-submit for a filter to trigger the filter,
and then sort the filtered table, i would be really appreciative.
Also, if anyone has a better way to do this, let me know, and I am
open to change. I should note that I have no experience with js or
AJAX.

Thanks so much.