SAP C4C SDK: How to Invoke a query on click of an item in the List to display within the same AdvancedListPane?

We have custom BO as QN and QN Item. They are 2 different BO’s. Where QNItem BO has an element as QN ID.

So the relation is 1 QN has * QN items.

Every QN item has a field called Approve quantity and amount. In QN – OWL I need to perform a sum of all the approve quanity and amount for all its QN items and display it here. (in the box highlighted in red)

My idea was to Create query for the QNItem like this. So this retrieves all the items like this below snapshot.

When I execute this query, I get this result. I thought I will call this query and do a sum of the values and display it here on this field.

Question is:

On the OWL, there is no event triggered on click of an item in AdvancedListPane. So Im not sure how to call the query?

Any clues or suggestions please…

Thanks

Gayathri