Listbox Distinct selection using values from other listboxes

[#1]

I have a document that takes the list from two listboxes and selects the “selected” values from the two into a third listbox, all using different states.  So basically, LB1 and LB2 have a list of all available IDs.  When some values are selected in the “states” dimensions the values for the corresponding state’s ID lsitbox are selected.  I then have a button that when clicked selects the IDs in LB3 from LB1 and LB2 creating a unique list of values from both the LB1 and LB2 listboxes.

What I want to do now is create another listbox that only has the IDs that are selected in both LB1 and LB2 not a unique “full” list.

Here is a quick example…

LB1      LB2      LB3      LB4 (New)

1           2           1           2

2          7           2           7

7           12         7

10                     10

                         12

Is there a way to do this in QlikView?