Access values outside the ABAP user exit

When implementing a customer exit (i.e. field, user etc) have you ever wanted to be able to read additional field values available in the main SAP program but not available in your exit. Now with the use of field-symbols you can have access to any field available in the main SAP program. The code below demonstrates how this is done within a field exit on BSTNR which can be tested using transaction ME21. Information on creating field exits can be found here.

FUNCTION field_exit_bstnr.
*"----------------------------------------------------------------------
*"*"Local interface:
*"  IMPORTING
*"     REFERENCE(INPUT)
*"  EXPORTING
*"     REFERENCE(OUTPUT)
*"----------------------------------------------------------------------
* create field symbol
  FIELD-SYMBOLS: <status>.

* Assign value of variable from calling prog to field symbol
  ASSIGN ('(SAPMM06E)RM06E-BSART') TO <status>.

* Display value retrieved in message
* Note: Messages of type i and w are not allowed
  IF sy-subrc = 0.
    MESSAGE e003(zr) WITH <status> 'kkk'.
  ENDIF.

ENDFUNCTION.

Access values outside the SAP customer exit