How to change the place of the cursor (active record place) in a subgrid based on the selected record in the grid

Hi All and I need help.

I use NAV 2018 and VisualStudioCode+Al.

I created 2 temporary tables and inserting records on-fly (let's imagine I select the "Customer" + "Customer Ledger Entry" and insert record based on some conditions). We had a similar form in the old version of NAV.

next step - I created the Main page (type = Card) which has 2 sub-pages (based on 2 temporary tables above) and NAV is filtering CustomerTransactionLines subpage based on the selected record from CustomerAccountList subpage:

- part(CustomerAccountList; "Customer Account List")

- part(CustomerTransactionLines; "Customer Transaction Lines")
                    Provider = CustomerAccountList;
                    SubPageLink = "Customer No." = field ("No.");

NAV shows All data OK (the second subpage is filtered), but if I change the place of the cursor (change the record) in the subgrid CustomerAccountList  the current "active" (selected) list for CustomerTransactionLines sub-page is updated. But the (??) place of the cursor either like FILNDLAST or like FINDFIST. And the "selection" for the place is not predictable.

My idea was "to inform" the CustomerTransactionLines sub-page somehow that active record in the CustomerAccountList was changed.  But it is failed.

Any idea of how to do it?