How to Populate a listbox based on another listbox selection. Please help!

Question

Hi Experts,
     I have a requirement where I have two listboxs(dropdown list) in a selection screen. I have to populate the second listbox based on the selected item from the first listbox. How to do this?
I have created a listbox in a selection screen using
Parameters: p_soldto as listbox visible length 30 user-command chg,
            p_shipto as listbox visible length 30.
Then I have tried to look at the value of item selected  from first listbox in AT SELECTION-SCREEN OUTPUT, But I am not getting any value of p_soldto.
I think I am doing something wrong. I think I have to use some event handling like on selection of an item from listbox. But I don't see any such event handing in ABAP.
Please give me some code example.
Please help!
Thanks
Gopal

Answer 1

HI,
Check this program, it is using a list box and filling values into it at initilization event.
<b>REPORT ztest2.
TYPE-POOLS : vrm.
tables: bkpf.
DATA : values TYPE vrm_values.
DATA : wa LIKE LINE OF values.
PARAMETERS : list_box(10) TYPE c AS LISTBOX VISIBLE LENGTH 10.
PARAMETERS: dd type bkpf-BSTAT user-command abc.
select-options: a for bkpf-bukrs MODIF ID buk.
select-options: b for bkpf-belnr MODIF ID SEL.
at selection-screen output.
  If list_box = 2.
    loop at screen.
      if screen-group1 = 'SEL'.
        screen-input = 0.
        modify screen.
      endif.
    endloop.
  endif.
INITIALIZATION.
  wa-key = '1'.
  wa-text = 'Orange'.
  APPEND wa TO values.
  wa-key = '2'.
  wa-text = 'Red'.
  APPEND wa TO values.
  wa-key = '3'.
  wa-text = 'Blue'.
  APPEND wa TO values.
  wa-key = '4'.
  wa-text = 'Gray'.
  APPEND wa TO values.
  CALL FUNCTION 'VRM_SET_VALUES'
       EXPORTING
            id              = 'LIST_BOX'
            values          = values
       EXCEPTIONS
            id_illegal_name = 1
            OTHERS          = 2.</b>
Regards,