it appears that you want a blank line between entries with the same item ID.
what I would do is create an additiondetail section, that is blank, and I would suppress the whole section unless the item ID changed. You can check the if the id has changed in a couple of ways...I usually use a variable, but I have seen, and it would probably be cleaner using a 'next' or 'previous' to compare with the next or prior record.
What I am getting at is a blank line that is displayed occasionally so that the spacing is what you want.
HTH