add/remove button between listboxes

Hi, i'm trying to move the item from listbox1 to listbox2 (i'm populating the item from database and put into the listbox1 anyway) by using add / remove buttons. When I click add button, the selected item will move to listbox 2 , as soon as I click remove, the item will go back to listbox1 from listbox2. The item must be gone in listbox1 as soon as i click add button and appear in listbox2 and vice versa.

this is my code :

Private Sub cmdadd_Click()
If lstSelect.ListIndex <> -1 Then
lstMove.AddItem lstSelect.List(lstSelect.ListIndex)
lstSelect.RemoveItem (lstSelect.ListIndex)
End If
End Sub

Private Sub cmdrenove_Click()
If lstMove.ListCount > 0 Then
    If lstMove.ListIndex <> -1 Then
        lstMove.RemoveItem lstMove.ListIndex
        lstSelect.AddItem lstMove.ListIndex
    End If
End If
End Sub

can anyone tell me what's wrong with this code ?? I think the add button works well, but the remove button doesn't . Can anyone help me ?