I am looking for a pool chemistry calculator that (hopefully) could be ported to an iPhone or iPad. Richard Falk's Pool Equations Spreadsheet looks like a possibility; however, it appears very complex. Does anyone know if there is any documentation (other than the scattered notes on the spreadsheet) on the proper use of his calculator?

I am very confused about Initial and Goal values; both of which change depending on which buttons are pressed.

Any help would be appreciated.