If I choose (Stage) Sourcing > (Task) opens only RFQ, Negotiation options; start and end dates are filled manually.
Once I fill in the end date for Negotiation (final task of stage Sourcing), stage cell is automatically updated with QA (next in line), and new dates fields become blank, to be filled manually again.
Operation repeats with QA stage/task drop list.
This means that, per row, I have information related to one product; the only thing that changes is the stage, task and dates.