I have a form with a TabControl and a few pages . On the Main Page of the TabControl ,I show details from the Parent (Say Customer) and on one of the Pages, I have a Grid whic shows Transactions from a Child Table (Say Invoices).

Where is the best place to put code (on the Activate of the Page ) so that :

If I have that Transaction Page Visible, the Transactions are refreshed when I navigate to a new  Customer on the Main Page of the tabControl

If I have the Main Page Visible and I navigate to a new customer, I dont want to waste time querying the Transactions (because I may not actually want to see the transactions) , but if I 'click' on the Transactions Page, i want to query the Child Table, and just refesh the grid at that point

(The main reason i dont want to 'Refresh' the children each time I change customer, is because there could be hundreds of transactions, and more oftren than not I will just be traversing the Customers , and looking at the data from the Customer table, and will not be interested in the transactions at all)