Create Custom Attachment in User Descision

Hello Everyone,

I am relatively new to the workflow world. Before raising this question i have gone through all the previous threads but could not find an answer to my problem. Here is my problem

I have created a business object as below to create an attachment

      zswr_att_header-file_type = 'B'.

      zswr_att_header-file_name = 'PurchaseOrder'.

      zswr_att_header-file_extension = 'PDF'.

      zswr_att_header-language = 'EN'.

      CALL FUNCTION 'SAP_WAPI_ATTACHMENT_ADD'

        EXPORTING

          workitem_id = workitemid

          att_header  = zswr_att_header

          att_bin    = lv_file_xstring

        IMPORTING

          att_id      = zswr_att_id.

    ENDIF.

  ENDIF.

ENDIF.

swc_set_element container 'ZSWR_ATT_ID' zswr_att_id.

swc_create_object sofm 'SOFM' zswr_att_id-doc_id.

swc_set_element container 'SOFM' sofm.

however when this attachment is passed back to the workflow it shows there is no instance of this. How do i create an instance so that i can get the attachment in  my workflow?

Thanks

Ashok