how to read workflow container elements in class methods

hi,

1. i  created two workflow container elements in workflow.

2. i am using below code to read container elements inside the class methods but i am unable to populate data from conatiner

     INCLUDE cntn01_oo.

      DATA:lv_purord TYPE ebeln,

       lv_relcod TYPE frgco,

       lv_test TYPE char20 VALUE 'TEST PROG'.

  swc_container container.
  swc_create_container container.
  swc_get_element container 'PURCAHSEORDER1' lv_purord.
  swc_get_element container 'RELEASECODE'   lv_relcod.
  swc_set_element container 'TEST'   lv_test.

3. if i am not using below statements it is showing syntax error container not found .

   swc_container container.

   swc_create_container container.

please guide me if anything wrong and please answer .