I think there should be a tool that can take two proportions from the same row (so four columns: numerator population 1, denom population 1, numerator population 2, denom population 2) and return the z-score between the two groups, with a check box to select the desired confidence level.
We monitor quarter-over-quarter changes in satisfaction diagnostics for some of our surveys, and we report the change in Top 2 box % (answers of very satisfied or somewhat satisfied); and we typically only investigate the changes that are statistically significant at a 95% confidence interval.
I have to write about 8 different formulas within the formula tool to get me the z-scores between the groups I'm investigating. A z-score tool would greatly reduce my workload!