Answer
Yes — implement this as a Custom Logical Unit holding the base data you want displayed, the same fields the Quick Report currently produces, plus a genuine persisted custom field for each additional calculated/user-entered column, including the markup value itself, presented together on a Custom Overview Page. Even though the markup value itself doesn't need to be meaningful long-term business data, it still needs to be backed by a real custom field to support an editable grid-style entry screen in IFS, since there's no built-in mechanism for a purely in-memory, non-persisted editable grid tied directly to a Quick Report's output — the calculated result can then be written from that custom page into the related Sales Contract Item as needed.