How could I create two list boxes with connected selection?

[Matsa]

Hello , 

I need to create 2 list boxes .when I select an element in one list box it will be added to second listbox ( add as selected value)
 I tried to create second listbox with this expression: (first list box with ATT1)

=Aggr( Only({<[ATT1] = P(ATT2])>} ATT2), ATT2)

But the element will add to second list box while there are deselected.

Do you have any Idea for implementing my requirement.

Thank you in advance.

Regards,

Matsa

[Brett_Bleess]

Mat, no idea if this one will help or not, but it is something:

https://community.qlik.com/t5/QlikView-Layout-Visualizations/How-to-use-conditional-view-with-getfie...

This will also re-kick your post up to the top, so someone else may see it and offer up something else that works better, but I wanted to try to find you something here.  The only other thing that came to mind was the Always One Selected option in the 2nd list box, but I am betting that would mess things up when you clear things...  You may need to potentially throw a sample QVW together on this one to attach too, as sometimes that can help folks better understand things and come up with possibilities for you.

Regards,
Brett