It may just be GoogleDocs not being Excel, but you currently have an =IF([condition],[formula],0) setup for your iterative attacks. If you're actually using 0 in Excel (and it's not simply an artifact of Google), it will say 0% rather than remaining blank when the BAB condition is not met. While technically remaining true (you won't hit with attack 2 because you won't make it), it seems misleading.
That said, it looks fine for what it covers, but I also notice it doesn't calculate the number of attacks correctly.
The formula you use, ROUNDDOWN((B32/4)+1,0), scales iterative attacks at an accelerated rate from what is actually the case. Iterative attacks scale every 5 levels after 1, not every 4, and not every 4th level (or 5th), but rather each Nth level after 1 (5th level after = 6th) so you should use ROUNDDOWN((1+(B32-1)/5),0)