No. Fling does damage depending on the held item that the user has when they use the move, after Fling is used the item is gone, even if the target was protected by a move like Protect. However, the user will keep the item in online battles or in places such as the Battle Maison and Battle Tree.
When a Pokemon holds an Iron Ball and uses Fling, the power will be 130.
For a list of what items will do what amount of damage, you can look here
(I would post the Bulbapedia link because it doesn't require you to have to toggle the lists of items and the corresponding damage, but according to the website the page may be missing items.)
