title: Set value of dependent listbox in AT SELECTION-SCREEN
body: <p>I created a report with some selections using ABAP screen listbox.</p>
  
  <pre><code>REPORT z_prueba.
  
  TYPE-POOLS: vrm.
  
  DATA : name    TYPE vrm_id,
         list    TYPE vrm_values,
         value   LIKE LINE OF list,
         aux(85) TYPE c.
  
  DATA: i_grupo     TYPE STANDARD TABLE OF ztart_mto_1,
        i_material  TYPE STANDARD TABLE OF ztart_mto_2,
        i_aux       TYPE STANDARD TABLE OF ztart_mto_2,
        wa_grupo    TYPE ztart_mto_1,
        wa_material TYPE ztart_mto_2,
        wa_aux      TYPE ztart_mto_2.
  
  
  SELECTION-SCREEN BEGIN OF BLOCK cab WITH FRAME TITLE tcab.
  PARAMETERS:
    grupo TYPE ztart_mto_1-grupo AS LISTBOX VISIBLE LENGTH 80 USER-COMMAND gr.
  SELECTION-SCREEN END OF BLOCK cab.
  
  SELECTION-SCREEN BEGIN OF BLOCK art WITH FRAME TITLE tart.
  PARAMETERS:
    articulo TYPE ztart_mto_2-refn AS LISTBOX VISIBLE LENGTH 80 USER-COMMAND art.
  SELECTION-SCREEN END OF BLOCK art.
  
  INITIALIZATION.
    tcab = 'Grupo de artículos'.
    tart = 'Artículo del grupo'.
  
    SELECT * INTO TABLE i_grupo FROM ztart_mto_1.
    CLEAR list.
    REFRESH list.
    LOOP AT i_grupo INTO wa_grupo.
      CLEAR value.
      CLEAR aux.
      CONCATENATE wa_grupo-grupo ` - `  wa_grupo-denom INTO aux.
      value-key = wa_grupo-grupo.
      value-text = aux.
      APPEND value TO list.
    ENDLOOP.
  
    name = 'grupo'.
  
    CALL FUNCTION 'VRM_SET_VALUES'
      EXPORTING
        id     = name
        values = list.
  
    CLEAR name.
    CLEAR list.
    CLEAR i_grupo.
    CLEAR wa_grupo.
  
  AT SELECTION-SCREEN ON VALUE-REQUEST FOR grupo.
    IF grupo = ''.
  
      "HERE I NEED TO PUT THE VALUE OF articulo IN BLANK
  
    ELSE.
  
      SELECT * FROM ztart_mto_2 WHERE grupo = @grupo INTO TABLE @i_material.
  
      LOOP AT i_material INTO wa_material.
        CLEAR value.
        CLEAR aux.
        CONCATENATE wa_material-refn ` - `  wa_material-descr INTO aux.
        value-key = wa_material-refn.
        value-text = aux.
        APPEND value TO list.
      ENDLOOP.
  
      name = 'articulo'.
  
      CALL FUNCTION 'VRM_SET_VALUES'
        EXPORTING
          id     = name
          values = list.
  
      articulo = ''.
  
      CLEAR grupo.
      CLEAR aux.
      CLEAR name.
      CLEAR list.
      CLEAR i_material.
      CLEAR wa_material.
      REFRESH i_material.
  
    ENDIF.
  </code></pre>
  
  <p>I need to change the value of <code>articulo</code> when the value of <code>grupo</code> is blank.</p>
  
  <p>When I've set a value for <code>grupo</code> and <code>articulo</code> and then set <code>grupo</code> to blank <code>articulo</code> is not changing</p>
  
  <p><img src="https://i.stack.imgur.com/CLrMg.png" alt="enter image description here"></p>