def observe_my_select

@to_be_updated = params[:processarc]
  @service = Service.find(:all ,:conditions =>{:Service_name =>   params[:processarc]})
  @servicesubentities = Servicesubentities.find(:all ,:conditions =>{:service_id => @service})
  render :partial => 'input_field'    
end

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partial: _input_field.html.erb
<select name="servicesubentity_name" id="id"> <%= options_from_collection_for_select(@servicesubentities, :id, :servicesubentity_name,:selected => “servicesubentity_name”) %>
</select>

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