Please find the link below that will give you the theory behind the tool
http://www.sigma-cap.com/wwwhome2/warren_buffet.htm
please use if you find it useful only as a stock screener, In one glance you can get some critical info about the status of the company and stock price.
1. it tells you the current PE and historical PE highs and lows
2. gives the ROE, PBV, Dividend yield current and historical
3. With little additional work one can calculate EPS growth rate
4. A simple Projection based on historical growth
5. and a projection based on ROE and reinvested capital
In most cases the model tells you clearly reasons for a stock quoting at the price that it is quoting
Please bear in mind
1. All the calculations are based on historical values and with no consideration for future
2. Needs adjustments if the stock had bonus/split in the last 7 years
3. You will need many years to realize if the model works or not
Regards
Suresh Kumar