then I want a method that is executed for create / edit actions, that use @my_var1, and can set variables available in the view.

tests_controller.rb

class TestsController < ApplicationController
  before_filter :execute_me, :only => :index

  def index
    @my_var2 = translate_me('ES', @my_var)
  end

 private
 
 def execute_me
   @my_var = 'Hi'
 end
 
 def translate_me(some_language, some_value)
   if some_language=='ES'
    'hola'
   end
 end 

end
end