You are both incorrect, as I've already pointed out in my warstory. Every last site I've gone to (except Serebii, which is well known for being unreliable and its hard to tell whether it says it says that it stays stagnant or implies it keeps degrading).
In Gen IV, protect had an inaccuracy cap of 12.5%. The change to Gen V has actually removed that cap, so consecutive protects are less likely to work than ever.
As for a good damage calculator for B/W, the one in
this thread is excellent.
EDIT: For clarification, just go to
this Bulbapedia page; it explains it in the easiest to understand way of all the sites I've visited: