Public Class Form1 Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick ListBox1.Items.Add(ListBox1.Items.Count) End Sub End Class What this does is add to our listbox the number of items in the listbox each time the tick event executes which we set earlier to 1000 or every second. Step6: Run the program by pressing F5 keyword on your keyboard and notice how the numbers get added to the listbox. With the help of the scroll bar you can see the numbers till end.