Precalculation - Allow to change Item Material Code instead to have delete and insert new one material

Actually is not possible to change an item code material in precalculation, we can only delete and insert a new one material position.

In the precalculation window if the user need to replace a item material code instead other, the user must to delete a material position and insert a new one, would be nice to allow to change the item code in the same material position.

Regards