custom list in Purchase order part lines

Hi Rakesh, 

Sorry for a very late answer. But here is for what it’s worth. Assuming that you want to connect TrackingInformation against the Purchase Order Lines Part list records. 

1. The association is made between the custom TrackingInformation and CustomerOrderLines entity is then wrong. The Purchase Order Lines Part list is of PurchaseOrderLinesPart entity, and you should create an association between those two. 
   
   You can control this by inspecting the metadata returned to the client when navigating to the page, using the chrome explorer. Projection/Entities/PurchaseOrderLinePart/Arrays. If your association is created correctly there should be a TrackAssoc in the arrays dictionary.

2. The Association that you create will end up in the projection metadata on the PurchaseOrderLinesPart entity (array) not on the TrackingInformation. So when you add the list for TrackingInformation to your page 
   Bindname: <element you bind to> i.e., PurchaseOrderLinesPartList 
   Property: <relation> i.e., TrackAssoc

If this is setup this way. Data for TrackingInformation should change as you select different records in the PurchaseOrderLinesPartList. I’m not quite certain how this works if you keep your TrackingInformation outside the tab control though. Might be that you need the keep the TrackInformation list under Purchase… in the tab. On the other hand, with this connection that would be quite logical UI wise for the user (IMO)