Gear Comparison Calculator

I've decided I need a keep-it-simple calculator for comparing old gear to new gear. The idea is just to compare stats on two items to see how much it will shift your uncrushability. When you pull it up you only need to fill in the yellow squares, put the rating of your old item in the first yellow row, and the rating of the new item in the second yellow row.

I'd like people to review it, and let me know if I have any typographical or logic errors. I tried to gleam these formulas off the forums.

If this is a success, I'll probably write a little Java Applet that does the same thing.

http://files.mperry.net/ratingcalc.xls

Edit:
I made a few minor changes including: fixing the parry formula, added a few other stats to help get the full picture of your upgrade, and put the new item on the first yellow line.

Edit again @ 2:13 EST:
My formulas were too complicated, and like I said I am keeping this simple. I posted it back up with simplified formulas and a conversation table to help level/class differences.
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