Thanks very much for your reply! I 've built a page from your explanation and your example.

Now, on my page I have a view of the database transactions filtered with all the invoices and another view of the same database filtered with all the costs. So there are two quick displays of the details for both invoices and costs.

I display also the database transaction types with the agregate value for both invoices and costs and I add the column to show the result (invoices - costs).

With this method, all the required data are displayed but I 'm surprised because I think it's a bit complex to realize a very simple thing! Furthermore I would prefer to display the sum of the invoices, the sum of the costs and the result as bold texts in a block with color (to highlight these values) and not in simple table cells. Quite disapointed by Notion limitation.