inrement combobox value or index based on another (both have same values)

hi
i have 2 comboboxes (dropdowns) both have same values cb1 & cb2 values are (john, kay, sara) ..
i need to have cb2 automatically have a plus one value of cb1 based on (cb1) selectedIndex change .

meaning once a user selects "John" from cb1, then automatically cb2 will not show john but the very next item which is "Kay". and so on.

i tried (on cb1's selected index changed )

if cb1.selectedIndex > 0 then
cb2.selectedIndex += cb1.selectedIndex +1
==========did not work===============

then tried

            For i = 0 To cb1.Items.Count - 1
                   lbltest5.Text = cb2.Items.Item(i)
            Next

but it adds the last value of cb1 to cb2 and nothing else.
any ideas would be much appreciated
thanks