Get top level refID in planned production orders explosion tab in AX 7

Hello,

I have created a new field in between Number and reference type in the below screenshot and I am trying to display the topLevel reference itemId. 

In order to achieve it, I am trying to get the top level refId. 

Please see the following Link for better understanding. I want the same to be also done in AX7.

https://dynamicsuser.net/ax/f/developers/94168/get-top-level-refid-in-planned-production-orders-explosion-tab/493404#493404

Thanks