cascading combos

Hello,
I want to connect and relate two combo so that when the item is selected in the first combo, the values of the second combo are changed.

; Suppose, I have four list :



(setq lst_City (list "A" "B" "C" )

            lst_A (list "A1" "A2" "A3" )

            lst_B (list "B1" "B2" "B3" "B4" )

            lst_C (list "C1" "C2"  )

)



(COND ((= (DCL-COMBOBOX-GETCURSEL ABC_Fin/Form1/ComboBox1)

	  0

       ) ;_ end of equal

       (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	      (DCL-COMBOBOX-ADDLIST

		ABC_Fin/Form1/ComboBox2

		lst_A

	      ) ;_ end of dcl-ComboBox-AddList

       ) ;_ end of progn

      )

      ((= (DCL-COMBOBOX-GETCURSEL ABC_Fin/Form1/ComboBox1)

	  1

       ) ;_ end of equal

       (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	      (DCL-COMBOBOX-ADDLIST

		ABC_Fin/Form1/ComboBox2

		lst_B

	      ) ;_ end of dcl-ComboBox-AddList

       ) ;_ end of progn

      )

      (T

       (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	      (DCL-COMBOBOX-ADDLIST

		ABC_Fin/Form1/ComboBox2

		lst_C

	      ) ;_ end of dcl-ComboBox-AddList

       ) ;_ end of progn

      )

) ;_ end of cond

My problem is that when I click on an item in the first Combo, nothing is visible in the second Combo.
What can I do with this problem?
Please advice me .

Hi friends,
Despite the fact that no one responded to this post,I was able to solve this issue below :

(DEFUN c:ABC_Fin/Form1/ComboBox1#OnSelChanged

       (ItemIndexOrCount Value /)

  (COND



    ((AND (= ItemIndexOrCount 0) (= Value (NTH 0 lst_City)))

     (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	    (DCL-COMBOBOX-ADDLIST

	      ABC_Fin/Form1/ComboBox2

	      lst_A

	    ) ;_ end of DCL-COMBOBOX-ADDLIST

     ) ;_ end of progn

    )

    ((AND (= ItemIndexOrCount 1) (= Value (NTH 1 lst_City)))

     (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	    (DCL-COMBOBOX-ADDLIST

	      ABC_Fin/Form1/ComboBox2

	      lst_B

	    ) ;_ end of DCL-COMBOBOX-ADDLIST

     ) ;_ end of progn

    )

    ((AND (= ItemIndexOrCount 2) (= Value (NTH 2 lst_City)))

     (PROGN (DCL-COMBOBOX-CLEAR ABC_Fin/Form1/ComboBox2)

	    (DCL-COMBOBOX-ADDLIST

	      ABC_Fin/Form1/ComboBox2

	      lst_Rusta_C

	    ) ;_ end of DCL-COMBOBOX-ADDLIST

     ) ;_ end of progn

    )

  ) ;_ end of cond

) ;_ end of defun

If One of the members has a better suggestion, please tell me.
I am not English and apologize for the mistakes in the conversations.
Thank you and have a good time .