excel vba - how to add item to a combobox on button click? -

i want add item combobox found in excel worksheet text box located in user form when button clicked.i see value added combobox become empty when close , reopens workbook.can 1 me handling this?

thank u you're fast response first

thank both feedback , correction.let me make more clear concern

1. create workbook , save xlsm.
2. on first worksheet define user name follows: name: dn_cmb_items range: =""
3. using developer ribbon add excel (not activex) combobox onto worksheet1 , set list-by-range dn_cmb_items
4. open vba editor , add user form workbook, name frm_add_cmb_item , set showmodal false.
5. drop text box form , name tb_item_text.
6. drop button form, name cmb_add , context menu choose view code. creates click event handler.
7. implement handler follows:

     private sub cmb_add_click()       dim v_r range, v_n name       set v_n = names("dn_cmb_items")       if v_n.value = "="""""         v_n.value = "=" & worksheets(1).name & "!$a$1:$a$1"         v_n.referstorange.value = tb_item_text.text       else         set v_r = v_n.referstorange         set v_r = v_r.cells(v_r.rows.count + 1, 1)         v_r.value = tb_item_text.text         v_n.value = "=" & worksheets(1).name & "!$a$1:" & v_r.address(true, true)       end if     end sub 

8. drop onto workshet button, create/set macros in workbook. implement created macros code frm_add_cmb_item.show.
9. in vba editor debug menu choose compile. save vbaproject workbook. that's coding.
10. switch worksheet, show form.
11. now when enter textbox, click cmb_add button, new item added a column @ end changing value of dn_cmb_items assigned combobox on worksheet. see screenshorts attached:

initial state:

1 added:

2 added:

ps have ready workbook code. should upload it?