If you get stuck doing this, take a look at a stickied hunter simulator on the WoW forums - it uses pre-entered item stats (and must have taken a jurassic age to write) to trigger a vlookup function. It also allows you compare up to 8 sets of gear which is great for working out how each set of gear will react to a talent change. Only thing is that I don't think it estimates the effect of Improved Aspect of the Hawk.
It can be found in this thread
http://forums.worldofwarcraft.com/th...=1#post1066563
Any other comments on the sheet would be interesting as I have used it, rather than Lactose's, for most of my observations (i.e. some rather skimpy work on the theoretical point at which 0/21/30 outperforms 5/31/15).