I've created an Excel spreadsheet for charting various chemicals in my pool and thought others might find it useful.
It contains a section for recording measurements of Chlorine, pH, TA, TH and CYA, and a section for recording the addition of Chlorine, and Muriatic Acid.
The sheet has four line charts which chart the data you input in the measurement sections.
The first chart, called "Chem Tracking" shows your chlorine level and ph over time and also places dots on the graph which indicate added chlorine and muriatic acid along how many ounces you added. Of course, you might have to customize this with your specific chemicals (I will probably never need to raise my pH as our tap water is at 8.2), but it's a good template for graphing your pool's health history.
The other charts are simple line charts that track, ph,TA,TH, and CYA over time.
I've never owned a pool until now, so I'm sure I will find ways to improve this later on.
You can download the Excel file, here. (Excel 2003 Format)
To use it, just delete the example data from the "measurements" and "chem log" sheets and input your own. Unless I made some stupid mistake, a graph should automatically show the data you input.