I am currently writing a ...

I am currently writing a spreadsheet in Excel (I love spreadsheets!) for designing a facultative lagoon, a complete effluent irrigation onto a woodlot (flow rate, tree spacing, parameter levels, SAR, population projections, flow projections, evaporation, trans evaporation, overlap percentages of the above ground sprinkler systems, number of trees, tree species, etc...) its gonna take me about 3 months to complete each but when I am done, the user will simply have to enter in known parameters on the front page and all the hidden pages will complete the complex calculations. I am sorry that I don't have an easy answer for you except that each engineer should develop their own spreadsheet as rules and regulations are different in different countries...even if you had mine you would still need to tweak it to suit your needs.