title: Update BSEG-ZUONR with Function Module
body: <p>I successfully change <code>BKPF-BKTXT</code> with <code>FM CHANGE_DOCUMENT</code> but why can't I change <code>BSEG-ZUONR</code> with <code>FM CHANGE_DOCUMENT</code> too?</p>
  
  <p>Here's the <code>FM CHANGE_DOCUMENT</code>:</p>
  
  <pre><code>CALL FUNCTION 'CHANGE_DOCUMENT'
    TABLES
      T_BKDF           = t_bkdf
      T_BKPF           = t_bkpf
      T_BSEC           = t_bsec
      T_BSED           = t_bsed
      T_BSEG           = t_bseg
      T_BSET           = t_bset
  *   T_BSEG_ADD       =
            .
  </code></pre>
  
  <p>Here's the code to change <code>BKPF-BKTXT</code> (succeeded):</p>
  
  <pre><code>wa_t_bkpf-mandt = sy-mandt.
  wa_t_bkpf-bukrs = '1000'.
  wa_t_bkpf-gjahr = gjahr_import.
  wa_t_bkpf-belnr = belnr_import.
  wa_t_bkpf-bktxt = zuonr_import.
  APPEND wa_t_bkpf TO t_bkpf.
  </code></pre>
  
  <p>Here's the code to change <code>BSEG-ZUONR</code> (failed):</p>
  
  <pre><code>wa_t_bseg-mandt = sy-mandt.
  wa_t_bseg-bukrs = '1000'.
  wa_t_bseg-gjahr = gjahr_import.
  wa_t_bseg-belnr = belnr_import.
  wa_t_bseg-buzei = '1'.
  wa_t_bseg-zuonr = zuonr_import.
  APPEND wa_t_bseg TO t_bseg.
  </code></pre>