After add new item reload the listbox

Question

I have a listbox.I need to update(reload) it when add new item by the user.Plz help me

this is listbox data binding

 public void Filllistbox()
        {
            //InitializeComponent();
            listBox1.DataSource = omni.NEWUSERs;
            listBox1.DisplayMember = "FNAME";
            listBox1.ValueMember = "USERID";
           
        }

I need to reload this listbox after add new user
thankz